Data transfer scheme
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There are two types of data transfer schemes: synchronous and asynchronous. Synchronous uses a common clock signal where the processor addresses a device at t0, the device places data on the bus at t1, and the processor reads the data at t2. Asynchronous replaces the clock with ready and accept control signals, where the ready signal indicates the device is ready to accept data and the accept signal confirms the data was received.
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COA asynchronous data transfer
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USART
1. To make asynchronous serial communication using a microcontroller's USART, the transmitter must configure the baud rate generator and enable transmission by writing data to the transmit register, while the receiver must configure the baud rate generator and enable reception to read incoming data from the receive register.
2. Key steps include setting the SPBRG register and BRGH bit to determine the baud rate, enabling the serial port and transmission/reception, handling 9-bit data if needed, and checking status registers for transmission completion or errors.
3. Asynchronous serial communication allows microcontrollers to transmit data bit by bit over a single line using start and stop bits for synchronization instead of a separate clock line.
INTERFACING WITH INTEL 8251A (USART)
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
Interrupt
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The document discusses the 8251 programmable communication interface chip. It provides 3 key points:
1. The 8251 is a USART (Universal Synchronous Asynchronous Receiver Transmitter) chip that allows for serial communication and converts parallel data from the CPU to serial data and vice versa.
2. It has sections for data buffering, read/write control, modem control, transmission and reception. It uses control and status registers to program the chip for synchronous or asynchronous modes.
3. The chip can operate in asynchronous or synchronous modes. In asynchronous mode, it adds start and stop bits for transmission and looks for start/stop bits for reception. In synchronous mode, it uses sync characters
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The document discusses the Universal Synchronous Asynchronous Receiver Transmitter (USART) which is a serial communication device. It describes the USART's synchronous and asynchronous communication modes and includes a block diagram and explanation of its transmitter, receiver, and pin sections. The USART receives parallel data from a microprocessor and transmits it serially or vice versa while including start/stop bits and potentially parity bits. It was commonly used to connect two microprocessor systems or for modem interfacing.
8251 usart programmable communication interface by aniket bhute
This document provides an overview of the 8251A USART chip, including:
- It is a programmable peripheral designed for serial communication that converts parallel data from the CPU to serial and vice versa.
- It has sections for the data bus buffer, read/write control logic, modem control, transmitter and receiver.
- The transmitter accepts parallel data and converts it to serial, while the receiver accepts serial data and converts it to parallel for the CPU.
- It has control, status and data registers that are accessed via various control signals to read/write data and control the chip's operation.
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Universal Asynchronous receiver transmitter is a device used for serial communication in various devices.
28. 8251 programmable communication interface
The 8251 programmable communication interface chip allows microprocessors like the 8085 to communicate serially. It contains buffers and registers that can convert parallel data from the microprocessor to serial data for transmission to I/O devices and vice versa. The 8251 has a mode word register that specifies characteristics like baud rate and parity, and a command word register that enables transmission and reception. It also has status and data registers for reading communication status and transferring data.
UART(universal asynchronous receiver transmitter ) PPT
UART – Stands for Universal Asynchronous Receiver Transmitter It is a piece of hardware that acts as a bridge between the processor and the serial communication protocol or port (RS-232). It performs parallel – to – serial data conversion at the transmitter side and serial – to – parallel data conversion at the receiver side.Asynchronous serial communication.
A serial communication can be done using fewer wires as compared to its parallel counterpart. It is a cheapest communication device with a single wire for transmitting the data and another wire for receiving. When the high-speed data transfer is not required UART is used. In a simple serial communication, 3 pins are used: TxD, RxD and GND.
At Transmission side (i.e. From Microcontoller), one can write data into UART Data Register (e.g. UART0_DR) by using software code.
These 8 bits of data from Data Register is passed to Tx FIFO Buffer. After that, the data is sent out(one at a time) from Tx Shift Register.
TxFIFO flag = 1 (Buffer full) TxFIFO flag = 0 (not full - Software can write to Data Register)
At Receiver end, there is Rx FIFO Buffer.
RxFIFO Empty flag = 1 (Buffer is empty) RxFIFO Empty flag = 0 (Buffer has data to be read)
A frame is the unit of transmission in serial communications
Start bit: To declare the start of transmission.
Data bits: 4,5,6,7, or 8 bits of useful data bits.
Parity bit : To check for transmission errors.
Stop bit: To declare end of frame
Parity bit is used to check the integrity of a frame and signal if an error occurred during transmission.
It is an extra bit added to the end of a frame.
Even parity :The number of ‘1’ symbols inside a frame must always be even.
Odd parity : The number of ‘1’ symbols inside a frame must always be odd
The configuration settings at both ends of Txd and Rxd:
Full or half-duplex operation
Data length
Start/Stop bits
Transmission speed.
EX:-198 = 11000110
Transmission speed
Common speed = 9600 bits/sec
1/9600 = 104 us.
After detecting start it will count 104us and complets start bit.
Then begins sampling the input bits after 52us with equal count of 104us between each bit untill the next stop bit with high pulse.
Advantages
Requires minimum wires
No need for clock or any other timing signal.
Parity bit ensures basic error checking.
Disadvantages
Size of the data in the frame is limited.
Can connect only two devices at a time
Speed for data transfer is less compared to parallel.
Transmitter and receiver must agree to the rules of transmission and appropriate baud rate must be selected.
if we are looking for a device to device serial communication then UART proves itself the best as it is easy to deal with and also widely used in many peripheral devices.
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This document discusses various data transfer schemes between I/O devices and memory in a computer system. It describes DMA which allows direct transfer of data from I/O to memory without CPU involvement. It also covers programmed I/O which uses the CPU to control data transfers for small amounts of data. Asynchronous and synchronous transfer methods are explained along with handshaking techniques for asynchronous transfers between devices running at different speeds. Interrupt-driven I/O is also summarized which uses interrupt requests from I/O devices to signal the CPU to service a transfer.
8251 a basic
The document discusses the 8251A USART chip, which can be used for both asynchronous and synchronous serial communication. It describes the basic components and functions of the 8251A chip, including its transmitter and receiver sections that convert parallel to serial data and vice versa. The document also explains the differences between asynchronous and synchronous serial communication and covers various control signals and registers used by the 8251A for data transfer and interfacing with external devices like modems.
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Input output organization
The document discusses various aspects of I/O organization in a computer system. It describes the input-output interface that provides a method for transferring information between internal storage and external I/O devices. It discusses asynchronous data transfer techniques like strobe control and handshaking. It also covers asynchronous serial transmission, different modes of data transfer like programmed I/O, interrupt-initiated I/O, and direct memory access (DMA).
USART
1. To make asynchronous serial communication using a microcontroller's USART, the transmitter must configure the baud rate generator and enable transmission by writing data to the transmit register, while the receiver must configure the baud rate generator and enable reception to read incoming data from the receive register.
2. Key steps include setting the SPBRG register and BRGH bit to determine the baud rate, enabling the serial port and transmission/reception, handling 9-bit data if needed, and checking status registers for transmission completion or errors.
3. Asynchronous serial communication allows microcontrollers to transmit data bit by bit over a single line using start and stop bits for synchronization instead of a separate clock line.
INTERFACING WITH INTEL 8251A (USART)
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.
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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
Interrupt
Interrupts allow input/output devices to alert the processor when they are ready. When an interrupt request occurs, the processor saves its context and jumps to an interrupt service routine. It then acknowledges the interrupt and restores its context before returning to the original instruction. Processors have mechanisms for prioritizing interrupts and enabling/disabling them to avoid infinite loops or unintended requests.
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2) The RS-232 standard for serial communication interfaces between DTE and DCE devices. It specifies voltage levels, connector types, and signal functions.
3) Common interface chips like the 8250/16450/16550 UART used for asynchronous communication and flow control between devices.
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This document discusses different techniques for transferring data between input/output (I/O) devices and the central processing unit (CPU). It describes programmed I/O, interrupt-driven I/O, and direct memory access (DMA). Programmed I/O involves the CPU continuously checking I/O device status, wasting CPU time. Interrupt-driven I/O improves efficiency by allowing devices to interrupt the CPU when ready. DMA is most efficient as it transfers data directly between memory and I/O devices without using the CPU, which then regains control after the transfer.
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Serial data transfer
This document discusses serial vs parallel communication and provides details on asynchronous and synchronous serial communication. It also describes the basic components and terms used in serial communication including start bits, stop bits, and baud rate. Finally, it outlines the four operating modes of the 8051 serial port including simple shift register mode, standard UART mode, multiprocessor mode, and a variable baud rate mode.
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The document discusses the 8251 programmable communication interface chip. It provides 3 key points:
1. The 8251 is a USART (Universal Synchronous Asynchronous Receiver Transmitter) chip that allows for serial communication and converts parallel data from the CPU to serial data and vice versa.
2. It has sections for data buffering, read/write control, modem control, transmission and reception. It uses control and status registers to program the chip for synchronous or asynchronous modes.
3. The chip can operate in asynchronous or synchronous modes. In asynchronous mode, it adds start and stop bits for transmission and looks for start/stop bits for reception. In synchronous mode, it uses sync characters
Input Output Organization
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.
8251 USART
The document discusses the Universal Synchronous Asynchronous Receiver Transmitter (USART) which is a serial communication device. It describes the USART's synchronous and asynchronous communication modes and includes a block diagram and explanation of its transmitter, receiver, and pin sections. The USART receives parallel data from a microprocessor and transmits it serially or vice versa while including start/stop bits and potentially parity bits. It was commonly used to connect two microprocessor systems or for modem interfacing.
8251 usart programmable communication interface by aniket bhute
This document provides an overview of the 8251A USART chip, including:
- It is a programmable peripheral designed for serial communication that converts parallel data from the CPU to serial and vice versa.
- It has sections for the data bus buffer, read/write control logic, modem control, transmitter and receiver.
- The transmitter accepts parallel data and converts it to serial, while the receiver accepts serial data and converts it to parallel for the CPU.
- It has control, status and data registers that are accessed via various control signals to read/write data and control the chip's operation.
UART
Universal Asynchronous receiver transmitter is a device used for serial communication in various devices.
28. 8251 programmable communication interface
The 8251 programmable communication interface chip allows microprocessors like the 8085 to communicate serially. It contains buffers and registers that can convert parallel data from the microprocessor to serial data for transmission to I/O devices and vice versa. The 8251 has a mode word register that specifies characteristics like baud rate and parity, and a command word register that enables transmission and reception. It also has status and data registers for reading communication status and transferring data.
UART(universal asynchronous receiver transmitter ) PPT
UART – Stands for Universal Asynchronous Receiver Transmitter It is a piece of hardware that acts as a bridge between the processor and the serial communication protocol or port (RS-232). It performs parallel – to – serial data conversion at the transmitter side and serial – to – parallel data conversion at the receiver side.Asynchronous serial communication.
A serial communication can be done using fewer wires as compared to its parallel counterpart. It is a cheapest communication device with a single wire for transmitting the data and another wire for receiving. When the high-speed data transfer is not required UART is used. In a simple serial communication, 3 pins are used: TxD, RxD and GND.
At Transmission side (i.e. From Microcontoller), one can write data into UART Data Register (e.g. UART0_DR) by using software code.
These 8 bits of data from Data Register is passed to Tx FIFO Buffer. After that, the data is sent out(one at a time) from Tx Shift Register.
TxFIFO flag = 1 (Buffer full) TxFIFO flag = 0 (not full - Software can write to Data Register)
At Receiver end, there is Rx FIFO Buffer.
RxFIFO Empty flag = 1 (Buffer is empty) RxFIFO Empty flag = 0 (Buffer has data to be read)
A frame is the unit of transmission in serial communications
Start bit: To declare the start of transmission.
Data bits: 4,5,6,7, or 8 bits of useful data bits.
Parity bit : To check for transmission errors.
Stop bit: To declare end of frame
Parity bit is used to check the integrity of a frame and signal if an error occurred during transmission.
It is an extra bit added to the end of a frame.
Even parity :The number of ‘1’ symbols inside a frame must always be even.
Odd parity : The number of ‘1’ symbols inside a frame must always be odd
The configuration settings at both ends of Txd and Rxd:
Full or half-duplex operation
Data length
Start/Stop bits
Transmission speed.
EX:-198 = 11000110
Transmission speed
Common speed = 9600 bits/sec
1/9600 = 104 us.
After detecting start it will count 104us and complets start bit.
Then begins sampling the input bits after 52us with equal count of 104us between each bit untill the next stop bit with high pulse.
Advantages
Requires minimum wires
No need for clock or any other timing signal.
Parity bit ensures basic error checking.
Disadvantages
Size of the data in the frame is limited.
Can connect only two devices at a time
Speed for data transfer is less compared to parallel.
Transmitter and receiver must agree to the rules of transmission and appropriate baud rate must be selected.
if we are looking for a device to device serial communication then UART proves itself the best as it is easy to deal with and also widely used in many peripheral devices.
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Similar to Data transfer scheme
Unit-4 (IO Interface).pptx
I/O subsystems: Input/output devices such as Disk, CD,ROM, Printer etc.; Interfacing with IO devices, keyboard and display interfaces; Basic concepts Bus Control, Read Write operations, Programmed IO, Concept of handshaking, Polled and Interrupt driven I/O, DMA data transfer
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This document discusses various data transfer schemes between I/O devices and memory in a computer system. It describes DMA which allows direct transfer of data from I/O to memory without CPU involvement. It also covers programmed I/O which uses the CPU to control data transfers for small amounts of data. Asynchronous and synchronous transfer methods are explained along with handshaking techniques for asynchronous transfers between devices running at different speeds. Interrupt-driven I/O is also summarized which uses interrupt requests from I/O devices to signal the CPU to service a transfer.
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The document discusses the 8251A USART chip, which can be used for both asynchronous and synchronous serial communication. It describes the basic components and functions of the 8251A chip, including its transmitter and receiver sections that convert parallel to serial data and vice versa. The document also explains the differences between asynchronous and synchronous serial communication and covers various control signals and registers used by the 8251A for data transfer and interfacing with external devices like modems.
8251 USART.pptx
The document discusses asynchronous and synchronous data transfer using the 8251A USART chip. It describes the basics of serial communication including synchronous vs asynchronous transmission. It provides details on the sections and functioning of the 8251A chip, including its transmitter, receiver, and modem control sections. The pin diagram and functions of the pins are also explained.
Computer Organisation and Architecture
The document discusses input-output organization and describes various input and output peripheral devices. It then covers input-output interfaces, how data is transferred asynchronously between devices and the CPU using handshaking, and different modes of data transfer including program-controlled, interrupt-initiated, and direct memory access. It also discusses how interrupts from multiple devices are handled using priority levels and interrupt vectors.
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An I/O interface consists of circuitry that connects input/output devices to a computer system. It has a data path that transfers data between the interface and device. This side is called a port and can be either serial or parallel. A parallel port transfers data simultaneously using multiple pins, while a serial port transmits data one bit at a time, making it convenient for long distances. Both parallel and serial ports contain buffers to store data and status flags accessed by the processor to determine if the buffer is full or empty. The interface also performs any necessary format conversions like parallel to serial for a serial port.
Input Output Operations
The document discusses various aspects of input and output devices and their interface with the central processing unit of a computer system. It describes how peripherals like keyboards, displays and printers are connected and controlled. It explains the different modes of data transfer between CPU and peripherals, including programmed I/O, interrupt-initiated I/O, and direct memory access. The document also covers topics like asynchronous and synchronous data transmission, handshaking, and hardware priority interrupts.
INTERFACE UNIT IV.pptx
The document discusses input-output (I/O) interfaces in computers. It provides details on:
1. I/O interfaces act as a hardware circuit between the CPU and I/O devices to synchronize data transfer.
2. There are differences between peripheral devices and CPUs in operation, data formats, and speeds that require special hardware (I/O interfaces) to resolve.
3. I/O interfaces contain registers to buffer input and output data and status information during transfers between CPUs and peripheral devices like keyboards, printers, and monitors.
Io organization
The document discusses input-output organization in computer systems. It describes peripheral devices, input-output interfaces, asynchronous data transfer methods like handshaking, direct memory access, interrupt-driven I/O, and the universal asynchronous receiver-transmitter chip. The input-output system allows communication between the computer and external devices by resolving differences in data rates and operating protocols.
Ch11.ppt
This document discusses input/output organization in computer systems. It describes:
1) Peripheral devices for input and output and how they connect to the computer via interface modules on an I/O bus.
2) Asynchronous data transfer methods like handshaking that allow communication between devices running at different speeds.
3) Memory-mapped I/O that uses memory addresses for I/O, improving flexibility over isolated I/O that has separate address spaces.
4) Asynchronous serial transfer of data one bit at a time using start and stop bits to delineate characters transferred.
Ca 2 note mano
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.
io orgnz.ppt
The document discusses various aspects of input-output organization in computer systems. It describes peripheral devices, input-output interfaces, asynchronous data transfer methods using handshaking, direct memory access, interrupt handling, and input-output processors. The key aspects covered are the interface between the computer and external devices, synchronization for asynchronous data transfer, and different modes of transferring data between memory and I/O devices.
20ME702– MECHATRONICS -UNIT-4.ppt
This document provides an overview of programmable logic controllers (PLCs). It describes the basic structure of a PLC including input/output modules, a central processing unit, memory, and a programming unit. The document outlines how PLCs are used for automation in industrial processes by replacing hardwired relay controls. It also discusses PLC programming using ladder logic and provides examples of logic functions, timers, counters, and data handling capabilities of PLCs. Selection factors for choosing a suitable PLC for an application are also mentioned.
Programmable logic Controlller ppt
This document provides an overview of programmable logic controllers (PLCs). It describes the basic structure of a PLC including input/output modules, a central processing unit, memory, and a programming unit. The document outlines how PLCs are used for automation in industrial processes by replacing hardwired relay controls. It also discusses PLC programming using ladder logic and provides examples of logic functions, timers, counters, and data handling capabilities of PLCs. Selection factors for choosing a suitable PLC for an application are also mentioned.
Unit 4-PROGRAMMABLE LOGIC INTERFACE-ME6702– MECHATRONICS
This document provides an overview of programmable logic controllers (PLCs). It describes the basic structure of a PLC including input/output modules, a central processing unit, memory, and a programming unit. The document outlines how PLCs are used for automation in industrial processes as a replacement for hardwired relay controls. It also discusses PLC programming using ladder logic and provides examples of logic functions, timers, counters, and data handling capabilities of PLCs. Selection factors for choosing a suitable PLC are presented.
Input output organization (1).pptx
This document provides an overview of asynchronous data transfer methods in computer organization and architecture. It discusses four types of asynchronous data transfer: source initiated without handshaking, destination initiated without handshaking, source initiated with handshaking, and destination initiated with handshaking. It also covers programmed I/O, interrupts, direct memory access (DMA), and their applications in computer systems.
Unit 4 ca-input-output
This document discusses input/output organization in computer systems. It describes peripheral devices for input and output, input/output interfaces that allow communication between peripherals and the CPU/memory, and various methods for transferring data asynchronously between independent devices or systems, including strobe control, handshaking, and serial transmission. Asynchronous data transfer is necessary because peripherals often operate at different speeds than the CPU and memory.
SAMPLE FOR MICRO PROGRAMMING CO_-_7th_UNIT.pdf
The document discusses the basic components and functioning of a computer's central processing unit (CPU). It describes the fetch-execute cycle where the CPU fetches instructions from memory, increments the program counter, and executes the instruction. It explains the role of various registers like the program counter, instruction register, and memory data register in executing instructions. The document also covers different CPU organizations like hardwired control, microprogrammed control, and register transfer level organization involving data transfers between registers. It provides examples of control sequences to perform arithmetic operations, memory reads/writes, and conditional branching.
interface
An I/O interface consists of circuitry that connects input/output devices to a computer system. It has a data path that transfers data between the interface and device bidirectionally. The interface contains a buffer, status flags, and address decoding circuitry. It also performs any necessary format conversions such as parallel to serial for serial ports, which transmit data one bit at a time for long distance communication, while parallel ports transfer data simultaneously using multiple pins and having a simpler circuit.
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Unit 4-PROGRAMMABLE LOGIC INTERFACE-ME6702– MECHATRONICS
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Data transfer scheme
- 1. DATA TRANSFER SCHEME There are two types of data transfer scheme: 1. Synchronous 2. Asynchronous
- 2. Synchronous input / output transfer • Common clock signal is used. • At time t₀ the processor places the device address on the address lines of system bus. • During time t₀-t₁, address device gets the address & it recognize that an input operation is requested.
- 3. CONTINUED… • At time t₁, address device places its data on the data bus. At the end of the bus cycle i.e, at t₂ the processor reads the data lines & loads the data from data bus into its input buffer. • For output processor places the output data on data line. • At t₁ - Device reads the data line and load data into its data buffer. • At t₂ - Output have been received by the IO device and the cycle ends.
- 4. ASYNCHRONOUS INPUT/OUTPUT TRANSFER • The clock line replaced by two control signal ready and accept. • For input operation, processor places the address & sets the control lines to perform the input operation. • Ready line activated – Addressed device ready to accept data. • Addressed device place data on data accept line activated. • Processor load data on input buffer.
- 5. CONTINUED… For output operation: • Processor places the address, data and sets the control line to perform the output operation. • It then indicates the addressed device that it has send data by activating Ready signal. • The addressed device reads data into its input buffer when it receive ready signal. It then indicates that it has done so by the Accept signal.