By Muhammad Ali Mazidi, Rolin McKinlay, Danny Causey Ch. 2- Assembly Lang - PIC The PIC Microcontroller and Embedded Systems:  Using Assembly and C for PIC18 By Muhammad Ali Mazidi, Rolin McKinlay, Danny Causey

http://microdigitaled.com/PIC/Software/PIC_tools.htm Install MPLAB Install C18 Read tutorials from - http://microdigitaled.com/PIC/PIC_books.htm

Finish!!!? Now work at home n learn – based on the concepts of Intel 8086’s Assembly Language =======

Working Register

Only one! WREG – Working REGister is same as Accumulator in other microprocessors WREG us used for all arithmetic and logic instructions

MOVLW instruction MOVLW  move 8-bit data into the WREG reg. MOVLW k  Move literal value of k into WREG L  Literally – a number must be used Similar to immediate value of 8086’s assembly language MOVLW 25H  Move value 25H into WREG

MOVLW ‘L’ stands for literal Immediate value concept of other microprocessor ‘W’ for WREG MOVLW  move a literal value to WREG reg.

ADDLW

ADDLW Add ‘k’ to register WREG Put the result back in the WREG

WREG & ALU using literal value

MOVLW 5h MOVLW 05h MOVLW 00000101 ;in binary Moving a value larger than 255 (FF in hex) into the WREG register will truncate the upper byte and cause a warning in the .err file

2.2: File Register File register == data RAM == data memory == (general-purpose-reg. + special-function-reg.) Data memory space is different from program (code) memory

Data RAM == special-function-reg + general-purpose-reg Special-fn.reg. [SFR] for specific functions, e.g., ALU status Timers Serial communications I/O ports ADC Etc.

SFR… Function of each SFR is fixed by the CPU designer at the time of the design – as it is used for control of the microcontroller or peripheral 8-bit registers No. of locations in the file reg.? 7 to over a hundred more timers in a PIC, the more SFR reg. it has

Data RAM == special-function-reg + general-purpose-reg GPR / RAM Used for data storage and scratch pad 8 bits wide The space that is not allocated for SFRs – typically is sued for GPR

File reg. size [in bytes] PIC File register = SFR + GPR PIC12F508 32 bytes 7 25 PIC16… 80 12 68 PIC18F452 1792 256 1536

GPR RAM vs. EEPROM GPR – internal data storage, used by the CPU EEPROM – as an add-on memory, can add externally to the chip

File register & access bank in PIC18 PIC18 family can have a max of 4096 (4k = 212) bytes So, address range of the file reg. = 000h ~ FFFh File reg. is divided into 256-byte banks So, 4069/256 = 16 banks At least one bank for the file reg. – called access bank

256-byte access bank  two 128 bytes sections = GPR & SFR The 128 bytes – from locations 00H to 7FH – as General-purpose reg. used for read/write storage Scratch pad For storing data & parameters by PIC18 programmers & C compilers The other 128 bytes – from locations F80H to FFFH – as special-function reg.

So far for PIC MOVLW ADDLW Literal WREG

2.3: Using instructions with the default access bank MOVWF  it tells the CPU to move (in reality, copy) the source reg. of WREG – to a destination in the file reg. (F) So, the location (new) in file reg. will have the same value as reg. WREG. F – file reg. – stands for a location in the file reg. W – WREG

Move to SFR MOVWF PORTA MOVLW 55H ;WREG = 55H ; move the contents of WREG  into SFR reg. called PORTA MOVLW 55H ;WREG = 55H MOVWF PORTB ;copy WREG to Port-B MOVWF PORTC ;copy WREG to Port-C . PortB, PortC, and PortD are part of the special function reg. They can be connected to the I/O pins of the PIC mic.

Q: Can literal values directly into SFR? Move to GPR Move [copy] contents of WREG GPR/RAM MOVLW 99H ;WREG=99H MOVWF 0H ;move [copy] WREG contents to location 0h … Cant move literal [immediate] values directly into the general-purpose RAM locations in the PIC18. They must be moved there via WREG. Q: Can literal values directly into SFR?

ADDWF ADDWF fileReg, D ; =[WREG] + [fileReg] Sources: ADDLW 15H ; =15h + [WREG] ADDWF fileReg, D ; =[WREG] + [fileReg] Sources: Content of WREG fileReg: Content of file register (special or general) Destination: D  indicates destination bit If D = 0, destination of the result is WREG, or If D = 1, destination is file register