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![Program ROM
• ROM is used to store programs (program or code ROM)
• PIC 18 program ROM
• Flash [letter F for this]
• OTP (One Time Programmable) [letter C for this]
• Masked (during fabrication process)](https://image.slidesharecdn.com/lecture03basicsofpic-190107151825/75/Lecture-03-basics-of-pic-5-2048.jpg)
![PIC Status Register
• C (carry flag)
• This is set whenever there is a carry out from D7 bit (8th bit)
• This is affected after 8-bit addition and subtraction
• DC (digital carry flag) [Auxiliary Carry Flag]
• This bit is set whenever if there is a carry from D3 to D4 (during add and sub)
• This is used for BCD arithmetic
• Z (zero flag)
• If the result of arithmetic or logical operation is zero then z=1, otherwise (z=0)
for non-zero result.](https://image.slidesharecdn.com/lecture03basicsofpic-190107151825/75/Lecture-03-basics-of-pic-42-2048.jpg)
Uploaded byVajira Thambawita
Lecture 03 basics of pic
The document provides an overview of the PIC18 microcontroller features, including its RISC architecture, memory types (ROM, RAM, EEPROM), and assembly language programming concepts. It details the use of registers like the WREG and the file register, instruction types, and assembler directives. Additionally, it discusses the program counter and performance enhancement methods for microprocessor design.
In this document
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Introduction to the PIC microcontroller lecture.
Highlights of PIC18 microcontrollers include RISC architecture, chip features, ROM, RAM, EEPROM, timers, ADC, USART.
A simple illustration of the structure of PIC microcontrollers.
Details about the program ROM types used in PIC18: Flash, OTP, and Masked.
Explanation of data storage: RAM for temporary data, EEPROM for critical data.
Overview of PIC peripherals including ADC, timers, and USART.
Introduction to PIC architecture and assembly language programming.
WREG as a central 8-bit register for arithmetic and logic in PIC.
How to use the WREG register for data manipulation, including MOVLW and ADDLW instructions.
Description of file registers, including SFR and GPR in data memory space.
Instructions for moving data between WREG and file registers.
Using ADDWF to add data stored in registers with examples.
ALU instructions involving WREG and file registers.
Instructions for toggling port SFRs and decrementing file register contents.
MOVF copies data between WREG and file registers, while MOVFF enables direct transfer.
Explanation of the PIC status register and its flags - carry, overflow, zero, and negative.
Description of how status flags affect program flow through conditional branches.
Formats for representing data in PIC: hex, binary, decimal, and ASCII.
Introduction to assembler directives including EQU, SET, ORG, END.
Further assembler directives including #include and configuration settings.
Guidelines for creating labels in assembly language, emphasizing uniqueness and meaning.
Overview of the structure of assembly language programs.
Steps involved in creating a program for PIC microcontrollers, with examples.
Description of the program counter (PC) function and its significance in instruction execution.
Explanation of why PIC microcontrollers use Harvard architecture.
Details on instruction sizes in PIC18, with examples of common instructions.
Overview of methods to enhance processing power in microcontrollers, including clock frequency and architecture.
Key features of RISC architecture applicable to PIC microcontrollers.
Invitation to try using MPLAB IDE for programming PIC microcontrollers.
Summary of key concepts presented in the lecture regarding PIC microcontrollers.
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Lecture 03 basics of pic
- 1.
- 2. PIC18 features • RISCarchitecture • On-chip program (code) – ROM • Data RAM • Data EEPROM • Timers • ADC • USART and I/O ports
- 3.
- 5. Program ROM • ROMis used to store programs (program or code ROM) • PIC 18 program ROM • Flash [letter F for this] • OTP (One Time Programmable) [letter C for this] • Masked (during fabrication process)
- 6. Data RAM andEEPROM • RAM is for data storage. • RAM Space = General Purpose Register (GPR) + Special Function Registers (SFR) • Microchip website gives only the GPR size (because SFRs are fixed) • EEPROM: • To store critical data that does not need to be changed very often
- 7. PIC microcontroller pheripherals •ADC (10 bits) • Timers • USART (Universal Synchronous Asynchronous Receiver Transmitter)
- 8. PIC architecture andassembly language programming
- 9. The WREG register •The majority of PIC registers are 8 bits • Therefore, only one data type: 8 bits • Any data larger than 8 bits must be broken into 8-bits chunks. • WREG working register (only one) • WREG similar to accumulator in other microprocessors • WREG for all arithmetic and logic instructions
- 10. Understanding the WREGregister • MOVLW • Move 8-bit data into WREG register • Move a literal (L) value to WREG (W) • • • MOVLW 25H ;move value 25H (25 in hex) into WREG
- 11. Understanding the WREGregister • ADDLW • Add literal value K to WREG and put the result back to WREG • WREG = WREG + k
- 12. Understanding the WREGregister
- 13. Understanding the WREGregister
- 14. PIC FILE Register •File register data memory space read/ write (static RAM) • File register data RAM = SFR + GPR • SFR • Dedicated to special functions • ALU status • Timers • Serial communication • I/O ports • ADC • ….Etc.
- 15. PIC FILE Register(Contd..) • PIC SFRs are fixed and 8-bits • More SFR registers while PIC has more timers, ADCs etc • GPR (General purpose registers or RAM) • For data storage and scratch pad • Large GPR size means more difficulties in managing using assembly language • C compiler need more registers to handle parameters and perform job faster
- 16. PIC FILE Register(Contd..)
- 17. PIC FILE Register(Contd..)
- 18. PIC FILE Register(Contd..)
- 19. PIC FILE Register(Contd..)
- 20. Simple instructions withthe default access bank • MOVWF (W: WREG, F: file register) • This instruction tells to the CPU to move the source register of WREG to a destination in the file register. Special function registers
- 21. Simple instructions withthe default access bank GPR
- 22.
- 23.
- 24. More instructions • ADDWFfileReg, D SFR or GPR Adding the content of WREG and a file register Destination bit D=0 destination is WREG D=1 destination is file register
- 25.
- 26.
- 27.
- 28.
- 29. To make thingsless confusion Destination = WREG Destination = A file register
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- 32.
- 33. WREG, File Registersand ALU
- 34. ALU instructions usingboth WREG and fileReg
- 35. File register instructionsusing fileReg or WREG as destination
- 36. COMF instruction How towrite a program to toggle the SFR of Port B continuously forever?
- 37.
- 38. DECF • Decrement (subtractone) the content of fileReg and place the result in WREG or fileReg. • Destination is fileReg • Destination is WREG
- 39. MOVF • This mnemonicis intended to perform MOVFW. • MOVF fileReg, D • If D=0 it copies the content of fileReg to WREG • If D=1 fileReg is copied to itslef
- 40. MOVFF • Copies datafrom One location in fileReg another location in fileReg • Without going through the WREG
- 41. PIC Status Register •Flag register (status register)
- 42. PIC Status Register •C (carry flag) • This is set whenever there is a carry out from D7 bit (8th bit) • This is affected after 8-bit addition and subtraction • DC (digital carry flag) [Auxiliary Carry Flag] • This bit is set whenever if there is a carry from D3 to D4 (during add and sub) • This is used for BCD arithmetic • Z (zero flag) • If the result of arithmetic or logical operation is zero then z=1, otherwise (z=0) for non-zero result.
- 43. PIC Status Register •OV (overflow flag) • This is used for signed number arithmetic • N (Negative flag) • This is also used for signed number arithmetic • D7=0 N=0 result is positive • D7=1 N=1 result is negative • Not all instructions affect the flags
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- 46. Flag bits anddecision • Status flags are also called conditional flags. • Some instruction will make conditional jump (branch) based on the status of the flag bits.
- 47. PIC data formatrepresentation • Hex numbers If the value started with hex digit (A-F), then it must be preceded with zero.
- 48. PIC data formatrepresentation • Binary numbers (1 way) • Decimal numbers (2 ways) • ASCII character
- 49. Assembler Directives • Instructions What to do using the CPU • Directives (pseudo instructions) Directions to the assembler • Ex: EQU, SET, ORG and END • EQU • This is used to define a constant value or fixed address.
- 50. Assembler Directives • SET •This is used to define a constant value or fixed address. • SET and EQU directives are identical. • The value assigned by the SET directive may be reassigned later. • ORG • This is used to indicate the beginning of the address. (For both code and data). • The number that comes after ORG must be in hex.
- 51. Assembler Directives • END •This indicates to the assembler the end of source file (asm). • Last line of the program • LIST • This indicates to the assembler the specific PIC chip • We use LIST to state the target chip
- 52. Assembler Directives • #include •This tells the assembler to use the libraries associated with the specific PIC • _config • This tells the assembler the configurations bits for the target chip. • Don’t use incorrect config: it may meke the chip unusable • radix • This indicates whether the numbering system is hexadecimal or decimal. • Default is hexadecimal • For decimal
- 53. Rules for labels •Meaningful • Unique • Label consist of • upper and lower case letters • digits • ? • . • @ • _ • $ • First character alphabetic character • Don’t use reserved words (check the assembler for more details)
- 54. Structure of assemblylanguage • Four fields Optional fields Line of the code by name
- 55. Structure of assemblylanguage (Example- asm file)
- 56. Steps to createa program
- 57. Steps to createa program • Sample of PIC err file
- 58. Steps to createa program • Sample of List file
- 59. Program counter (PC) •Another important register in the PIC microcontroller. • The PC is used by the CPU to point the address of the next instruction to be executed. • The PC is incremented automatically. • The wider the PC CPU can access more memory locations • 14-bit PC 214 (16K) code (from 0000 to 3FFFH) • 16-bit 216 (64K) code (0000-FFFFH) • 21-bit 221 (2M) (000000-1FFFFFH)
- 60. Program counter (PC) •PIC18 on-chip ROM Size and address space
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- 62.
- 63. Executing a programbyte by byte Two bytes instructions Four bytes instruction
- 64. Executing a programbyte by byte • ROM contents
- 65. Why PIC useHarvard architecture?
- 66. Instruction size ofPIC 18 • MOLW (2 byte instruction) Opcode (8 bits) Literal value
- 67. Instruction size ofPIC 18 • ADDLW • MOVWF
- 68. Instruction size ofPIC 18 • MOVFF (4 bytes) • GOTO (4 bytes) Because, instructions are either 2 bytes or 4 bytes
- 69. Ways to increaseperformance • There are three ways available to microprocessor designers to increase the processing power of CPU • Increase clock frequency more power and heat dissipation • Use Harvard architecture very expensive and unrealistic for x86 architecture • Use RISC architecture Microchip used all three methods
- 70. Features of RISC •Feature 1: RISC processors have fixed instruction size. • Feature 2: Use large number of registers (at least 32 registers). • Feature 3: RISC processors have a small instruction set. • Feature 4: more than 95% of instructions are executed with only one clock cycle. • Feature 5: RISC processors have separate buses for data and code. • Feature 6: due to the small set of instructions, they are implemented using the hardwire method. (no more than 10% of transistors) • Feature 7: RISC uses load/store architecture. (no direct access to external memory for arithmetic operations, only via registers)
- 71. • Shall wetry MPLAB IDE?????
- 72.