The 8257 is a 4-channel direct memory access (DMA) controller. It is specifically designed to simplify the transfer of data at high speeds for the microcomputer systems. Its primary function is to generate, upon a peripheral request, a sequential memory address which will allow the peripheral to read or write data directly to or from memory. Acquisition of the system bus in accomplished via the CPU’s holds function or via cycle stealing function. It maintains the DMA cycle count for each channel and outputs a control signal for simplified sectored data transfers.8257 significantly simplifies the transfer of data at high speed between peripherals and memories. This work has been taken up to optimize and reduce area of DMA controller.
dma controller Direct Memory Access,The 8237 DMA Controller dmaAgathiSiva
An interrupt is an event that informs the CPU it needs to service an external request. Interrupts can come from internal faults, software, or external hardware sources. When an interrupt occurs, the CPU saves its state and jumps to an interrupt service routine (ISR) to handle the interrupt before returning to its previous task. The 8259 programmable interrupt controller (PIC) is used to manage interrupt requests from peripherals by masking interrupts, assigning priorities, and directing interrupts to the CPU. Direct memory access (DMA) allows peripherals to access memory directly without CPU intervention, improving data transfer speeds. Serial communication converts parallel data to serial transmission using universal asynchronous/synchronous receiver/transmitters (UART/US
The 8257 microprocessor is a 4-channel direct memory access (DMA) controller chip that can transfer data directly between I/O devices and memory without CPU involvement. Each of its 4 channels can be independently programmed to transfer up to 64kB of data via DMA and each channel has its own 16-bit address and 14-bit counter registers. It operates in either master or slave mode and uses priority resolving to determine which channel gets access to the bus for DMA transfers.
The document discusses the Intel 8257 DMA controller. It allows hardware subsystems to access main memory independently of the CPU, improving data transfer speeds. The 8257 has 4 channels that can service requests from I/O devices simultaneously. It interfaces between devices and the system bus, controlling direct memory access operations and arbitrating bus access. When an I/O device needs to transfer data, it sends a request to the 8257, which then coordinates the transfer directly between memory and the device without involving the CPU. This allows the CPU to continue processing without waiting for I/O, improving overall system efficiency and performance.
The Intel 8257 is a 4-channel direct memory access (DMA) controller that allows peripheral devices to directly access computer memory at high speeds. It generates memory addresses upon a peripheral request and controls the transfer of data between peripherals and memory without involving the CPU. The 8257 has priority logic to resolve requests from multiple peripherals and can transfer a block of data in a single burst, notifying the CPU when complete via a terminal count output. It represents a significant simplification and reduction in components for transferring data between peripherals and memory in microcomputer systems.
The document describes the Programmable DMA Controller 8237. It has 4 independent DMA channels that can transfer data between I/O and memory subsystems without CPU involvement. Each channel has registers to specify the starting memory address and transfer count. The controller's control logic manages the DMA cycles and status. It can prioritize multiple requests in either fixed or rotating priority modes.
The document discusses direct memory access (DMA) and DMA-controlled I/O. It describes how DMA allows direct access to memory while temporarily disabling the microprocessor. It also explains how disk and video systems often use DMA transfers. The document focuses on the basic operation of DMA, including the HOLD and HLDA control signals. It provides details on the 8237 DMA controller, including its pin definitions and programming. It explains how the 8237 facilitates high-speed data transfers between memory and I/O devices.
This document provides information on input/output organization and interfaces in a computer system. It discusses different I/O techniques like interrupts and direct memory access. Interrupts allow I/O devices to signal the processor when they need attention. Direct memory access enables high-speed transfer of data directly between I/O devices and memory without processor involvement. The document also describes common I/O bus standards like PCI, SCSI and USB and how they facilitate communication between devices and the computer.
The document discusses direct memory access (DMA) and the 8237 DMA controller chip. It provides the following key points:
1. DMA allows direct transfer of data between memory and I/O devices without processor involvement using HOLD and HLDA signals.
2. The 8237 DMA controller provides memory/I/O control signals and addresses to perform DMA transfers across 4 channels at up to 1.6MB/sec.
3. The 8237 contains registers like the current address and word count registers that control DMA transfers for each channel.
dma controller Direct Memory Access,The 8237 DMA Controller dmaAgathiSiva
An interrupt is an event that informs the CPU it needs to service an external request. Interrupts can come from internal faults, software, or external hardware sources. When an interrupt occurs, the CPU saves its state and jumps to an interrupt service routine (ISR) to handle the interrupt before returning to its previous task. The 8259 programmable interrupt controller (PIC) is used to manage interrupt requests from peripherals by masking interrupts, assigning priorities, and directing interrupts to the CPU. Direct memory access (DMA) allows peripherals to access memory directly without CPU intervention, improving data transfer speeds. Serial communication converts parallel data to serial transmission using universal asynchronous/synchronous receiver/transmitters (UART/US
The 8257 microprocessor is a 4-channel direct memory access (DMA) controller chip that can transfer data directly between I/O devices and memory without CPU involvement. Each of its 4 channels can be independently programmed to transfer up to 64kB of data via DMA and each channel has its own 16-bit address and 14-bit counter registers. It operates in either master or slave mode and uses priority resolving to determine which channel gets access to the bus for DMA transfers.
The document discusses the Intel 8257 DMA controller. It allows hardware subsystems to access main memory independently of the CPU, improving data transfer speeds. The 8257 has 4 channels that can service requests from I/O devices simultaneously. It interfaces between devices and the system bus, controlling direct memory access operations and arbitrating bus access. When an I/O device needs to transfer data, it sends a request to the 8257, which then coordinates the transfer directly between memory and the device without involving the CPU. This allows the CPU to continue processing without waiting for I/O, improving overall system efficiency and performance.
The Intel 8257 is a 4-channel direct memory access (DMA) controller that allows peripheral devices to directly access computer memory at high speeds. It generates memory addresses upon a peripheral request and controls the transfer of data between peripherals and memory without involving the CPU. The 8257 has priority logic to resolve requests from multiple peripherals and can transfer a block of data in a single burst, notifying the CPU when complete via a terminal count output. It represents a significant simplification and reduction in components for transferring data between peripherals and memory in microcomputer systems.
The document describes the Programmable DMA Controller 8237. It has 4 independent DMA channels that can transfer data between I/O and memory subsystems without CPU involvement. Each channel has registers to specify the starting memory address and transfer count. The controller's control logic manages the DMA cycles and status. It can prioritize multiple requests in either fixed or rotating priority modes.
The document discusses direct memory access (DMA) and DMA-controlled I/O. It describes how DMA allows direct access to memory while temporarily disabling the microprocessor. It also explains how disk and video systems often use DMA transfers. The document focuses on the basic operation of DMA, including the HOLD and HLDA control signals. It provides details on the 8237 DMA controller, including its pin definitions and programming. It explains how the 8237 facilitates high-speed data transfers between memory and I/O devices.
This document provides information on input/output organization and interfaces in a computer system. It discusses different I/O techniques like interrupts and direct memory access. Interrupts allow I/O devices to signal the processor when they need attention. Direct memory access enables high-speed transfer of data directly between I/O devices and memory without processor involvement. The document also describes common I/O bus standards like PCI, SCSI and USB and how they facilitate communication between devices and the computer.
The document discusses direct memory access (DMA) and the 8237 DMA controller chip. It provides the following key points:
1. DMA allows direct transfer of data between memory and I/O devices without processor involvement using HOLD and HLDA signals.
2. The 8237 DMA controller provides memory/I/O control signals and addresses to perform DMA transfers across 4 channels at up to 1.6MB/sec.
3. The 8237 contains registers like the current address and word count registers that control DMA transfers for each channel.
The 8237 DMA controller allows data transfer between I/O devices and memory without CPU intervention. It uses HOLD and HLDA signals to request and acknowledge DMA actions from the CPU. The 8237 contains registers like CAR, CWCR, CR, and SR to program DMA channel operations, addresses, counts, and status. It can perform DMA transfers at up to 1.6 MB/s across 4 channels. Modern systems integrate DMA controllers within chipsets rather than using discrete 8237 components.
This document provides an overview of the Intel 8257 Programmable DMA Controller. It describes how DMA operations are performed by allowing devices to directly access memory without CPU interference. It details the key features of the 8257 including its 4 channels, 16-bit addressing, and transfer modes. The document also includes diagrams of the 8257 architecture and pin connections. It concludes with advantages of DMA including faster transfer speeds and reduced CPU overhead, as well as disadvantages such as implementation costs.
The document discusses various data transfer techniques used in microprocessors, including synchronous, asynchronous, interrupt-driven I/O, DMA, and programmed I/O. It explains that synchronous transfer uses compatible speeds, asynchronous uses handshaking, interrupt-driven reduces processor waiting, DMA allows direct memory access to bypass the CPU, and programmed I/O uses the CPU to directly control I/O operations. It also covers serial vs parallel transmission and differences between them.
The document discusses direct memory access (DMA) and the Intel 8237 DMA controller. It describes how DMA allows high-speed transfer of data between memory and peripherals by bypassing the CPU. The 8237 controller uses HOLD and HLDA signals to request and gain control of address/data buses from the CPU during transfers. It initializes transfers via registers and decrements the word count register with each word transferred.
Direct Memory Access (DMA) allows certain hardware subsystems to access main system memory independently of the CPU. DMA controllers temporarily borrow the address, data, and control buses from the microprocessor to transfer data directly between an I/O port and memory locations. This allows fast transfer of data to and from devices while the CPU performs other tasks, improving overall system performance. DMA transfers can occur via block transfers where the DMA controller controls the bus for an extended period, or via cycle stealing where it uses the bus for one transfer then returns control to the CPU.
The document provides information about direct memory access (DMA) technology. It discusses that DMA allows certain hardware subsystems to access memory directly without processor intervention, allowing the processor to perform other tasks. It describes the basic DMA concept and that DMA is typically initiated by the CPU and uses a DMA controller. The DMA controller then controls the DMA operation and generates interrupts once complete. Common applications of DMA include disk controllers, video/sound cards, and memory-to-memory transfers.
IOSR journal of VLSI and Signal Processing (IOSRJVSP) is a double blind peer reviewed International Journal that publishes articles which contribute new results in all areas of VLSI Design & Signal Processing. The goal of this journal is to bring together researchers and practitioners from academia and industry to focus on advanced VLSI Design & Signal Processing concepts and establishing new collaborations in these areas.
Design and realization of microelectronic systems using VLSI/ULSI technologies require close collaboration among scientists and engineers in the fields of systems architecture, logic and circuit design, chips and wafer fabrication, packaging, testing and systems applications. Generation of specifications, design and verification must be performed at all abstraction levels, including the system, register-transfer, logic, circuit, transistor and process levels
The document discusses various methods for input/output (IO) in computer systems, including IO interfaces, programmed IO, interrupt-initiated IO, direct memory access (DMA), and input-output processors (IOPs). It describes how each method facilitates the transfer of data between the CPU, memory, and external IO devices.
The encoder circuit converts the key press signals from the keyboard switches into a binary code which is placed on the DATAIN lines. The interface also includes a debouncing circuit to filter out noise from the mechanical keyboard switches. When a valid key code is received, the interface asserts the SIN (strobe in) signal. The interface acts as a slave device on the bus - it asserts the slave ready signal in response to the master ready from the processor to indicate it can receive or transmit data.
This document provides an overview of input/output organization in computers. It discusses how computers can communicate with external devices through buses and interfaces. It covers different I/O techniques like programmed I/O, interrupt-driven I/O, and direct memory access. Interrupts allow devices to signal the processor when they need service. DMA controllers can transfer data directly between devices and memory without processor involvement. The document also addresses handling multiple devices, interrupt priorities, and simultaneous interrupt requests.
The document discusses Direct Memory Access (DMA) in microprocessor-based systems. It provides three key points:
1. DMA allows direct access to memory from I/O devices while temporarily disabling the microprocessor. This improves data transfer speeds between memory and I/O.
2. The 8237 DMA controller is used to control signals and address information during DMA transfers. It functions as a special-purpose microprocessor to enable high-speed data movement between memory and I/O.
3. DMA transfer speeds are determined by memory device or DMA controller speeds. The DMA controller can become the limiting factor, slowing down the system during transfers.
Here are the key tasks for initial configuration of a Cisco switch:
- Setting the enable and console passwords to secure access to privileged modes (Password must be between 4 and 8 characters)
- Setting the hostname to identify the switch
- Configuring the IP address and subnet mask on VLAN 1 to allow remote management via SSH/Telnet
- Configuring basic security settings like disabling unused ports, protocols, and services
- Configuring spanning tree protocol (STP) for redundancy and loop prevention in switched networks
- Verifying port status and connectivity using show commands
This document discusses input/output (I/O) organization in computer systems. It covers various I/O techniques including programmed I/O, interrupts, and direct memory access (DMA). Interrupts allow I/O devices to signal the processor asynchronously when data is ready to be transferred. DMA allows high-speed transfer of data between I/O devices and memory without processor involvement. The document also discusses I/O addressing techniques, I/O interface circuits, bus protocols, and arbitration when multiple devices seek to access the bus simultaneously.
This document discusses the fundamental concepts and organization of the central processing unit (CPU). It describes how the CPU fetches, decodes, and executes instructions through a multi-step process. It explains that the CPU uses a program counter to keep track of the next instruction, and increments it after fetching and decoding each one. It also details how the CPU performs operations like fetching data from memory, storing to memory, transferring between registers, and performing arithmetic/logic functions using the ALU.
Iaetsd implementation of hdlc protocol using verilogIaetsd Iaetsd
This document discusses the implementation of the HDLC protocol using Verilog. It describes the design of HDLC transmitter and receiver modules. The transmitter module encodes data, adds address and frame check sequence fields, and transmits the frame. The receiver module receives frames, detects flags and address, calculates the frame check sequence, and decodes the data. The modules were tested successfully in simulation and synthesized on an FPGA with low resource utilization. Implementing HDLC in Verilog provides flexibility and compatibility with different communication standards and interfaces.
This document discusses different types of data transfer modes between I/O devices and memory, including programmed I/O, interrupt-driven I/O, and direct memory access (DMA). It explains that DMA allows I/O devices to access memory directly without CPU intervention by using a DMA controller. The basic operations of DMA include the DMA controller gaining control of the system bus, transferring data directly between memory and I/O devices by updating address and count registers, and then relinquishing control back to the CPU. Different DMA transfer techniques like byte stealing, burst, and continuous modes are also covered.
1. Direct Memory Access (DMA) allows input/output devices to directly access main memory, bypassing the CPU to speed up memory transfers. This is managed by a DMA controller.
2. During a DMA transfer, the DMA controller gains control of the address bus, data bus, and control bus from the microprocessor to transfer data directly between an I/O port and memory.
3. The DMA controller has several options for transferring data, including cycle stealing for single byte transfers, burst mode for block transfers using address sequencing, and hidden DMA which occurs transparently when the CPU is not using the bus.
This document provides an overview of direct memory access (DMA), including its history, what it is, applications, channels, modes of operation, types, signals, advantages, and disadvantages. DMA allows fast transfer of data between storage devices and memory without involving the CPU, improving data transfer speeds. It has been a feature of PC architectures since the original IBM PC and is used for applications requiring high data transfer rates like storage, communication, and graphics.
The Intel 8257 is a 4-channel DMA controller that allows peripheral devices to directly access memory without involving the CPU. It has priority logic to handle requests from peripherals and issues memory addresses for read/write operations. Each channel has programmable address and count registers and can perform read, write, or verify transfers of up to 64kb of data independently. It uses a master/slave mode and rotating or fixed priority schemes to efficiently manage DMA requests and bus access for high-speed data transfers between peripherals and memory.
The Intel 8257 is a 4-channel direct memory access (DMA) controller that allows peripheral devices to directly access computer memory at high speeds. It generates memory addresses upon a peripheral request and controls the transfer of data between peripherals and memory without involving the CPU. The 8257 handles priority between multiple peripheral requests, maintains the transfer count for each channel, and notifies peripherals when a transfer is complete. It provides a significant reduction in components needed for DMA in microcomputer systems and greatly simplifies high-speed data transfers between peripherals and memory.
The Read/Write Control logic interfaces the 8251A with CPU, determines the functions of the 8251A according to the control word written into its control register.
It monitors the data flow.
This section has three registers and they are control register, status register and data buffer.
The active low signals RD, WR, CS and C/D(Low) are used for read/write operations with these three registers.
When C/D(low) is high, the control register is selected for writing control word or reading status word.
When C/D(low) is low, the data buffer is selected for read/write operation.
When the reset is high, it forces 8251A into the idle mode.
The clock input is necessary for 8251A for communication with CPU and this clock does not control either the serial transmission or the reception rate.ThesisScientist.com
The document discusses the 8251 USART chip, which converts parallel data to serial and vice versa. It describes asynchronous and synchronous communication methods. It provides details on the architecture of the 8251 including the read/write control logic, transmitter, receiver, and modem control sections. It also discusses initializing the chip by writing control words to set the mode, baud rate, parity, and enable transmission or reception.
The 8237 DMA controller allows data transfer between I/O devices and memory without CPU intervention. It uses HOLD and HLDA signals to request and acknowledge DMA actions from the CPU. The 8237 contains registers like CAR, CWCR, CR, and SR to program DMA channel operations, addresses, counts, and status. It can perform DMA transfers at up to 1.6 MB/s across 4 channels. Modern systems integrate DMA controllers within chipsets rather than using discrete 8237 components.
This document provides an overview of the Intel 8257 Programmable DMA Controller. It describes how DMA operations are performed by allowing devices to directly access memory without CPU interference. It details the key features of the 8257 including its 4 channels, 16-bit addressing, and transfer modes. The document also includes diagrams of the 8257 architecture and pin connections. It concludes with advantages of DMA including faster transfer speeds and reduced CPU overhead, as well as disadvantages such as implementation costs.
The document discusses various data transfer techniques used in microprocessors, including synchronous, asynchronous, interrupt-driven I/O, DMA, and programmed I/O. It explains that synchronous transfer uses compatible speeds, asynchronous uses handshaking, interrupt-driven reduces processor waiting, DMA allows direct memory access to bypass the CPU, and programmed I/O uses the CPU to directly control I/O operations. It also covers serial vs parallel transmission and differences between them.
The document discusses direct memory access (DMA) and the Intel 8237 DMA controller. It describes how DMA allows high-speed transfer of data between memory and peripherals by bypassing the CPU. The 8237 controller uses HOLD and HLDA signals to request and gain control of address/data buses from the CPU during transfers. It initializes transfers via registers and decrements the word count register with each word transferred.
Direct Memory Access (DMA) allows certain hardware subsystems to access main system memory independently of the CPU. DMA controllers temporarily borrow the address, data, and control buses from the microprocessor to transfer data directly between an I/O port and memory locations. This allows fast transfer of data to and from devices while the CPU performs other tasks, improving overall system performance. DMA transfers can occur via block transfers where the DMA controller controls the bus for an extended period, or via cycle stealing where it uses the bus for one transfer then returns control to the CPU.
The document provides information about direct memory access (DMA) technology. It discusses that DMA allows certain hardware subsystems to access memory directly without processor intervention, allowing the processor to perform other tasks. It describes the basic DMA concept and that DMA is typically initiated by the CPU and uses a DMA controller. The DMA controller then controls the DMA operation and generates interrupts once complete. Common applications of DMA include disk controllers, video/sound cards, and memory-to-memory transfers.
IOSR journal of VLSI and Signal Processing (IOSRJVSP) is a double blind peer reviewed International Journal that publishes articles which contribute new results in all areas of VLSI Design & Signal Processing. The goal of this journal is to bring together researchers and practitioners from academia and industry to focus on advanced VLSI Design & Signal Processing concepts and establishing new collaborations in these areas.
Design and realization of microelectronic systems using VLSI/ULSI technologies require close collaboration among scientists and engineers in the fields of systems architecture, logic and circuit design, chips and wafer fabrication, packaging, testing and systems applications. Generation of specifications, design and verification must be performed at all abstraction levels, including the system, register-transfer, logic, circuit, transistor and process levels
The document discusses various methods for input/output (IO) in computer systems, including IO interfaces, programmed IO, interrupt-initiated IO, direct memory access (DMA), and input-output processors (IOPs). It describes how each method facilitates the transfer of data between the CPU, memory, and external IO devices.
The encoder circuit converts the key press signals from the keyboard switches into a binary code which is placed on the DATAIN lines. The interface also includes a debouncing circuit to filter out noise from the mechanical keyboard switches. When a valid key code is received, the interface asserts the SIN (strobe in) signal. The interface acts as a slave device on the bus - it asserts the slave ready signal in response to the master ready from the processor to indicate it can receive or transmit data.
This document provides an overview of input/output organization in computers. It discusses how computers can communicate with external devices through buses and interfaces. It covers different I/O techniques like programmed I/O, interrupt-driven I/O, and direct memory access. Interrupts allow devices to signal the processor when they need service. DMA controllers can transfer data directly between devices and memory without processor involvement. The document also addresses handling multiple devices, interrupt priorities, and simultaneous interrupt requests.
The document discusses Direct Memory Access (DMA) in microprocessor-based systems. It provides three key points:
1. DMA allows direct access to memory from I/O devices while temporarily disabling the microprocessor. This improves data transfer speeds between memory and I/O.
2. The 8237 DMA controller is used to control signals and address information during DMA transfers. It functions as a special-purpose microprocessor to enable high-speed data movement between memory and I/O.
3. DMA transfer speeds are determined by memory device or DMA controller speeds. The DMA controller can become the limiting factor, slowing down the system during transfers.
Here are the key tasks for initial configuration of a Cisco switch:
- Setting the enable and console passwords to secure access to privileged modes (Password must be between 4 and 8 characters)
- Setting the hostname to identify the switch
- Configuring the IP address and subnet mask on VLAN 1 to allow remote management via SSH/Telnet
- Configuring basic security settings like disabling unused ports, protocols, and services
- Configuring spanning tree protocol (STP) for redundancy and loop prevention in switched networks
- Verifying port status and connectivity using show commands
This document discusses input/output (I/O) organization in computer systems. It covers various I/O techniques including programmed I/O, interrupts, and direct memory access (DMA). Interrupts allow I/O devices to signal the processor asynchronously when data is ready to be transferred. DMA allows high-speed transfer of data between I/O devices and memory without processor involvement. The document also discusses I/O addressing techniques, I/O interface circuits, bus protocols, and arbitration when multiple devices seek to access the bus simultaneously.
This document discusses the fundamental concepts and organization of the central processing unit (CPU). It describes how the CPU fetches, decodes, and executes instructions through a multi-step process. It explains that the CPU uses a program counter to keep track of the next instruction, and increments it after fetching and decoding each one. It also details how the CPU performs operations like fetching data from memory, storing to memory, transferring between registers, and performing arithmetic/logic functions using the ALU.
Iaetsd implementation of hdlc protocol using verilogIaetsd Iaetsd
This document discusses the implementation of the HDLC protocol using Verilog. It describes the design of HDLC transmitter and receiver modules. The transmitter module encodes data, adds address and frame check sequence fields, and transmits the frame. The receiver module receives frames, detects flags and address, calculates the frame check sequence, and decodes the data. The modules were tested successfully in simulation and synthesized on an FPGA with low resource utilization. Implementing HDLC in Verilog provides flexibility and compatibility with different communication standards and interfaces.
This document discusses different types of data transfer modes between I/O devices and memory, including programmed I/O, interrupt-driven I/O, and direct memory access (DMA). It explains that DMA allows I/O devices to access memory directly without CPU intervention by using a DMA controller. The basic operations of DMA include the DMA controller gaining control of the system bus, transferring data directly between memory and I/O devices by updating address and count registers, and then relinquishing control back to the CPU. Different DMA transfer techniques like byte stealing, burst, and continuous modes are also covered.
1. Direct Memory Access (DMA) allows input/output devices to directly access main memory, bypassing the CPU to speed up memory transfers. This is managed by a DMA controller.
2. During a DMA transfer, the DMA controller gains control of the address bus, data bus, and control bus from the microprocessor to transfer data directly between an I/O port and memory.
3. The DMA controller has several options for transferring data, including cycle stealing for single byte transfers, burst mode for block transfers using address sequencing, and hidden DMA which occurs transparently when the CPU is not using the bus.
This document provides an overview of direct memory access (DMA), including its history, what it is, applications, channels, modes of operation, types, signals, advantages, and disadvantages. DMA allows fast transfer of data between storage devices and memory without involving the CPU, improving data transfer speeds. It has been a feature of PC architectures since the original IBM PC and is used for applications requiring high data transfer rates like storage, communication, and graphics.
The Intel 8257 is a 4-channel DMA controller that allows peripheral devices to directly access memory without involving the CPU. It has priority logic to handle requests from peripherals and issues memory addresses for read/write operations. Each channel has programmable address and count registers and can perform read, write, or verify transfers of up to 64kb of data independently. It uses a master/slave mode and rotating or fixed priority schemes to efficiently manage DMA requests and bus access for high-speed data transfers between peripherals and memory.
The Intel 8257 is a 4-channel direct memory access (DMA) controller that allows peripheral devices to directly access computer memory at high speeds. It generates memory addresses upon a peripheral request and controls the transfer of data between peripherals and memory without involving the CPU. The 8257 handles priority between multiple peripheral requests, maintains the transfer count for each channel, and notifies peripherals when a transfer is complete. It provides a significant reduction in components needed for DMA in microcomputer systems and greatly simplifies high-speed data transfers between peripherals and memory.
The Read/Write Control logic interfaces the 8251A with CPU, determines the functions of the 8251A according to the control word written into its control register.
It monitors the data flow.
This section has three registers and they are control register, status register and data buffer.
The active low signals RD, WR, CS and C/D(Low) are used for read/write operations with these three registers.
When C/D(low) is high, the control register is selected for writing control word or reading status word.
When C/D(low) is low, the data buffer is selected for read/write operation.
When the reset is high, it forces 8251A into the idle mode.
The clock input is necessary for 8251A for communication with CPU and this clock does not control either the serial transmission or the reception rate.ThesisScientist.com
The document discusses the 8251 USART chip, which converts parallel data to serial and vice versa. It describes asynchronous and synchronous communication methods. It provides details on the architecture of the 8251 including the read/write control logic, transmitter, receiver, and modem control sections. It also discusses initializing the chip by writing control words to set the mode, baud rate, parity, and enable transmission or reception.
Read/Write control logic:
The Read/Write Control logic interfaces the 8251A with CPU, determines the functions of the 8251A according to the control word written into its control register.
It monitors the data flow.
This section has three registers and they are control register, status register and data buffer.
The active low signals RD, WR, CS and C/D(Low) are used for read/write operations with these three registers.
When C/D(low) is high, the control register is selected for writing control word or reading status word.
The DMA controller (8257) allows data transfer between I/O devices and memory without CPU involvement. It has 4 independent channels that can be programmed to transfer data via DMA read, write, or verify operations. The 8257 interfaces with the 8085 microprocessor by controlling address/data buses and generating control signals during DMA cycles when it acts as the bus master.
This presentation summarizes Direct Memory Access (DMA) and the Intel 8237 DMA controller. It defines DMA as transferring data between memory and I/O devices without CPU intervention, allowing high-speed transfers. The 8237 DMA controller handles DMA operations by controlling the address bus, data bus, and transfer modes. It has registers for addresses, counts, commands, modes and status. Transfer modes include single, block, demand, cascade and memory-to-memory.
8259 programmable PPI interfacing with 8085 .pptDrVikasMahor
This document provides information about the 8259A Programmable Interrupt Controller chip. It describes the chip's features such as supporting 8 levels of priority and being expandable up to 64 levels. It also explains how the chip works as an interrupt manager in a system, accepting requests from peripherals and determining which has highest priority to issue to the CPU. Block diagrams and explanations of the chip's registers and pins are provided.
DMA allows I/O devices to directly access memory without processor interference, allowing faster data transfer. It works by having the DMA controller send a hold request to the processor when a transfer is needed. The processor then relinquishes control of the buses, allowing the DMA controller to directly manage data movement between memory and I/O devices. The 8257 DMA controller has 4 channels that can each transfer up to 64kb of data independently using read, write, or verify operations.
This document discusses memory and I/O interfacing using microprocessors. It describes how memory and I/O devices are interfaced by connecting data and address lines, as well as control signals. It also discusses the three main types of data transfer between microprocessors and I/O devices: programmed I/O, interrupt-driven I/O, and direct memory access. Additionally, it provides information on common I/O interface chips like the 8255 Programmable Peripheral Interface and the 8279 Keyboard/Display Controller.
The 8251 is a serial communication interface chip that supports synchronous and asynchronous serial communication. It contains transmit and receive sections that convert parallel to serial and vice versa. It also has control registers for configuration. The 8251 interfaces with the 8085 microprocessor for serial communication with external devices through an RS-232 connector.
The 8251 is a Universal Synchronous/Asynchronous Receiver/Transmitter (USART) packaged in a 28-pin DIP made by Intel. It is typically used for serial communication and was rated for 19.2 kilobits per second signalling rate.
This document provides an overview of interfacing and input/output in embedded systems. It discusses buses, protocols, and the ISA bus. The key points covered are:
- Buses, wires, and ports are used for communication between processors, memory, and I/O devices. Protocols define rules for data transfer.
- Common I/O devices in embedded systems include analog/digital converters, displays, antennas, cameras, and touchscreens.
- Interfacing involves addressing devices, bus arbitration when multiple devices share a bus, and protocols for read/write operations.
- The ISA bus is described as an example, including its signals, memory/I/O cycles, and hand
This presentation summarizes the basic components and operation of an 8086 microcomputer system. It describes the CPU, memory, input/output devices, and three system buses (address, data, control). It then provides more detail on the clock generator, transceiver, and various ports. Diagrams are shown of a generic 8086 microcomputer block diagram and the 8086 pinout. Key signals such as A16-A19, RD, READY, and INTR are explained. The presentation provides a high-level overview of the basic 8086 system architecture and connections.
The document describes the 8259 programmable interrupt controller. It has 8 interrupt request lines that can be expanded to 64. It determines the priority of incoming interrupts and issues an interrupt signal to the CPU. Upon receiving an interrupt acknowledgement from the CPU, it provides vectoring data through 3 INTA pulses to direct the CPU to the appropriate interrupt service routine. It is programmed using initialization command words and operation command words to set interrupt priorities, masks, and modes.
The document compares the Intel 8085 and 8086 microprocessors. The 8086 is a faster, more powerful 16-bit processor compared to the 8-bit 8085. Key differences include the 8086 having a larger address bus and data bus, more transistors allowing for faster processing, additional registers and instructions, and features like memory segmentation and parallel processing that improved performance. The 8086 also used a pipeline architecture to more efficiently fetch and execute instructions.
The document discusses several topics related to microprocessor interfacing:
- It describes a Programmable Interrupt Controller (PIC) that helps a microprocessor handle interrupt requests from multiple sources by assessing priorities and informing the CPU.
- It then discusses data buses, buffers, and Direct Memory Access (DMA) controllers, which allow input/output devices to directly access memory with minimal CPU involvement.
- Finally, it introduces some common programmable logic devices (PLDs) like PALs, CPLDs, and FPGAs that can implement digital logic functions through programming. PLDs offer flexibility compared to fixed logic devices.
The document describes the von Neumann architecture, including its main components: main memory, arithmetic logic unit (ALU), control unit, CPU registers, and I/O equipment. The CPU consists of registers like the program counter, instruction register, and memory address register. The control unit interprets instructions and causes them to execute. Main memory stores both instructions and data, while the ALU performs arithmetic operations. I/O equipment is controlled by the control unit to input and output data.
visit: www.techbed.blogspot.com
I/O Memory Interface
Programmable, Interrupt initiated, DMA, Serial and Parallel Interfaces for data transfer
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3 ijcmes dec-2015-27-simulation of 8257 direct memory access controller (dma) using vhdl
1. International Journal of Civil, Mechanical and Energy Science (IJCMES) [Vol-1, Issue-1, Nov-Dec, 2015]
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Simulation of 8257 Direct Memory Access
Controller (DMA) Using VHDL
Vinod Kataria, Rajesh Kr. Saini
Reader, SKIT, Jaipur, Rajasthan, India
Abstract— The 8257 is a 4-channel direct memory access
(DMA) controller. It is specifically designed to simplify the
transfer of data at high speeds for the microcomputer
systems. Its primary function is to generate, upon a
peripheral request, a sequential memory address which will
allow the peripheral to read or write data directly to or from
memory. Acquisition of the system bus in accomplished via
the CPU’s holds function or via cycle stealing function. It
maintains the DMA cycle count for each channel and outputs
a control signal for simplified sectored data transfers.8257
significantly simplifies the transfer of data at high speed
between peripherals and memories. This work has been
taken up to optimize and reduce area of DMA controller.
Keywords— DMA controller, 8257, CPU, cycle stealing
I. INTRODUCTION
The 8257 DMA Controller is a peripheral chip originally
developed for the Intel 8085 microprocessor, and as such is a
member of a large array of such chips, known as the MCS-85
Family. This chip was later also used with the Intel 8086 and
its descendants. However, most often the functionality the
8257 offered is now not implemented with the 8257 chip
itself anymore, but is embedded in microcontrollers and
other VLSI chips. The 8257 chip itself is still in production.
Architecture and functional description of 8257 the
DMA Controller:
Fig. 1 Architectural representation of 8257
The 8257 is a programmable. Direct Memory Access
(DMA) device which, when coupled with a single Intel
8212 I/O port device, provides a complete four-channel
DMA controller for use in Intel microcomputer systems.
After being initialized by software, the 8257 can transfer a
block of data, containing up to 16.384 bytes. between
memory and a peripheral device directly,
Working:
Upon receiving a DMA transfer request from an enabled
peripheral, the 8257:
1. Acquires control of the system bus.
2. Acknowledges that requesting peripheral which is
connected to the highest priority channel.
3. Outputs the least significant eight bits of the memory
address onto system address lines A0-A7, outputs the most
significant eight bits of the memory address to the 8212 I/O
port via the data bus (the 8212 places these address bits on
lines A8-A15), and
4. Generates the appropriate memory and I/O read/ write
control signals that cause the peripheral to receive or
2. International Journal of Civil, Mechanical and Energy Science (IJCMES) [Vol-1, Issue-1, Nov-Dec, 2015]
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deposit a data byte directly from or to the addressed
location in memory.
The 8257 will retain control of the system bus and repeat
the transfer sequence. as long as a peripheral maintains its
DMA request. Thus, the 8257 can transfer a block of data
to/from a high speed peripheral (e.g.. a sector of data on a
floppy disk) in a single “burst”. When the specified number
of data bytes have been transferred, the 8257 activates its
Terminal Count (TC) output, informing the CPU that the
operation is complete.
The 8257 offers three different modes of operation: (1)
DMA read, which causes data to be transferred from
memory to a peripheral: (2) DMA write, which causes data
to be transferred from a peripheral to memory: and (3)
DMA verify, which does not actually involve the transfer of
data When an 8257 channel is in the DMA verify mode, it
will respond the same as described for transfer operations,
except that no memory or I/O read/write control signals will
be generated. thus preventing the transfer of data. The 8257.
however, will gain control of the system bus and will
acknowledge the peripheral’s DMA request for each DMA
cycle The peripheral can use these acknowledge signals to
enable an internal access of each byte of a data block in
order to execute some verification procedure, such as the
accumulation of a CRC (Cyclic Redundancy Code) check
word For example, a block of DMA verify cycles might
follow a block of DMA read cycles (memory to peripheral)
to allow the peripheral to verify its newly acquired data
II. DMA OPERATION
Single byte transfer:
single byte transfer is initiated by the 110 device raising the
DRO line of one channel of the 8257. If the channel is
enabled, the 8257 wilt output a HRO to the CPU. The 8257
now waits until a HLDA is received insuring that the
system bus is free for its use. Once HIDA is received the
DACK line for the requesting channel is activated (LOW).
The DACK line acts as a chip select for the requesting 110
device. The 8257 then generates the
read and write commands and byte transfer occurs between
the selected 110 device and memory. After the transfer Is
complete, the DACK line is set HIGH and the HRO line Is
set LOW to Indicate to the CPU that the bus is now free for
use. DRO must remain HIGH until DACK is issued to be
recognized and must go LOW before S4 of the transfer
sequence to prevent another transfer from occurring. (See
timing diagram.)
Consecutive Transfers :
If more than one channel requests service simultaneously y,
the transfer will occur In the same way a burst does. No
overhead is incurred by switching from one channel to
another. In each S4 the DRO lines are sampled and the
highest priority request is recognized during the next
transfer. A burst mode transfer in a lower priority channel
will be overridden by a higher priority request. Once the
high priority transfer has completed control will return to
the lower priority channel if its DRO is still active. No extra
cycles are needed to execute this sequence and the HRO
line remains active until all DRO lines go LOW.
Control Override.
The continuous DMA transfer mode described above can be
interrupted by an external device by lowering the HIDA
line. After each DMA transfer the 8257 samples the HLDA
line to insure that it Is still active, lilt is not active, the 8257
completes the current transfer, releases the HRQ line
(LOW) and returns to the idle state. If DRO lines are still
active the 8257 will raise the HRO line In the third cycle
and proceed normally .
The 8257 has a Ready input similar to the 8080A and the
8085k The Ready line is sampled in State 3. If Ready is
LOW the 8257 enters a wait state. Ready is sampled during
every wait state. When Ready returns HIGH the 8257
proceeds to State 4 to complete the transfer. Ready is used
to interface memory or 110 devices that cannot meet the bus
set up times required by the 8257.
The 8257 uses four clock cycles to transfer a byte of data.
No cycles are lost in the master to master transfer
maximizing bus efficiency. A 2MHz clock input will allow
the 8257 to transfer at a rate of 500K bytes/second.
Memory Mapped 110 Configurations
The 8257 can be connected to the system bus as a memory
device instead of as an I/O device for memory mapped I/O
configurations by connecting the system memory control
lines to the 8257’s I/O control lines and the system i/O
control tines to the 825Ts memory control tines.
This configuration permits use of the 8080s considerably
larger repertoire of memory instructions when reading or
loading the 8257s registers Note that with this connection,
the programming of the Read (bit 15) and Write (bit 14) bits
in the terminal count register will have a different meaning .
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Observation :
1. On giving the clock cycle all signal are presented on the
screen. We sees the following observations:
• All the signals are initialized.
• All the terminal counter registers are set to
“00000000000000”.
• The intermediate signal a,b,c,d are set to “0000”.
• Intermediate integers e, f, g, h are set to 0.
• We use the fixed priority in this project so the
priority signal is set to 0 for fix.
• All other signals are uninitialized with U.
Fig. 2 Signals after giving clock
2. Connecting the peripheral to the channel DMA sends the
Hold request to the CPU. On connecting the peripheral to
Channel 0 and channel 1. We observe the following
observations:
• Input from the peripheral is 1100 that is assigned
to the temo.
• This value of temo. is assigned to the DRQ as
1100.
• But channel 0 has highest priority. The
intermediate signal DRQ line will 1000.
• The HRQ line signal is generated to the
corresponding this DRQ signal will be 1000. Now
this signal goes to CPU for holding request.
Fig. 3 signals after requesting peripheral
3. DRQ line goes to CPU we observe following
observations:
• If CPU sees its data bus free it sends Hold
acknowledge to DMA.
• So the MSB of CPU memory register is set to
“00000000”.
• CPU generates the hold acknowledge (HLDA line)
1000. So the channel 0 is selected for data transfer.
• DMA acquires the control signal.
Fig.4 Signals after HLDA
4. DMA generates the Read and Write signal and data are
transfer between peripheral to CPU memory. DMA comes
4. International Journal of Civil, Mechanical and Energy Science (IJCMES) [Vol-1, Issue-1, Nov-Dec, 2015]
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to master mode. Data to be transferred is 80C0E0F0. It will
generate the IOR read signal. We observe the following
observations:
• When IOR=1 and IOW=0 then byte C0 read from
peripheral.
• When IOR=0 and IOW=0 then byte C0 is written
to CPU memory register.
• When IOR=1 and IOW=1 then byte C0 transferred
to DMA register from CPU memory.
• When IOR=0 and IOW=1 then byte C0 transferred
to peripheral.
Fig.4 Byte transferred to memory and Peripheral
The observation shown above completes one cycle of byte
transfer from memory to peripheral . Similar observations
can be taken for byte transfer from peripheral to memory.
Based on the above observations the following results were
obtained.
III. RESULT
From above observation we got a byte transferred from
peripheral to memory at the specified location.
Fig. 5 Result
Above observed screen indicates the byte transfer.
IV. CONCLUSION
In view of the above results of the DMA source code, we
can conclude that-
• The system simulated by us functions as 8257 IC chip
functions.
• Based on results, we conclude that the simulated
program implemented by us in VHDL is 8257 IC.
• During the simulation the byte is transferred to CPU
memory successfully.
• We know that as the application of microprocessors in
our technology intensive environment is increasing, so
we have to develop practical skills in the areas of
computer applications, networking, and interfacing. This
project 8257 DMA using VHDL is based upon
simulated test bench waveform analysis. After doing
this project we are able to provide manufacturing details
to fabricate the chip.
REFERENCES
[1] “The Practical Xilinx designer lab book”, Writer:
David Van den Bout Published by Xilinx
Corporation.
[2] “A VHDL Primer”. Writer: J. BhaskarPublished
by Pearson Education
[3] “Programmable DMA Controller 8257”. Published
by Intel.