a crc command

[richard]

I use this code to calculate crc's for various one wire things ds18b20 etc i would like to make a user command out of it
its limitation is in having all variables in bank 0 ,to avoid mucking about with bank switching, i assuming using these macros will make this a lot easier and more reliable
my question is what is the best way to go about it
should the crc var be a system var and the other just temps located anywhere ?
can you pass more than one var to a user command ?
can you pass optional var/s to a user command ?

code snippet:

GOTO BEGIN


asm
_CRCA
MOVLW 8
MOVWF _BC
YY MOVF _D,W
MOVWF _TMPS
MOVF _CRC,W
XORWF _TMPS,F
RRF _TMPS,F
BTFSS STATUS,C
GOTO XX
MOVLW 0X18
XORWF _CRC,F
XX RRF _CRC,F
RRF _D,F
DECFSZ _BC,F
GOTO YY
RETURN
ENDASM



BEGIN:


CRC VAR BYTE bank0 'CRC value system?
D VAR BYTE bank0 'input DATA to add to crc
BC VAR BYTE bank0 'temp var BIT COUNT
TMPS VAR BYTE bank0 'temp storage of byte to be crc'ed



main:
crc=0 'set crc to 0
some code
d= "z" ' a byte to crc
call crca
do some more code
d= "x" more data to crc
call crca
send crc to something

goto main '

[richard]

crc command

i was thinking something like this but its still going to need bank switching





GOTO over_BEGIN

USERCOMMAND "CRCc" ; Create a command called INCR


TempD VAR BYTE
TempBC VAR BYTE
TempTMPS var byte
;----[Main Code - Called by the macros]-------------------------------------


crca:

asm
_CRCa
MOVLW 8
MOVWF _TempBC
YY MOVF _TempD,W
MOVWF _TempTMPS
MOVF _CRC,W
XORWF _TempTMPS,F
RRF _TempTMPS,F
BTFSS STATUS,C
GOTO XX
MOVLW 0X18
XORWF _CRC,F
XX RRF _CRC,F
RRF _TempD,F
DECFSZ _TempBC,F
GOTO YY
RETURN
ENDASM










ASM
;----[crc a Byte]-----------------------------------------------------
CRCC?B macro Bin
MOVE?BB Bin, _TempD ; copy user var to TempVar
L?CALL _crca ; run the crc subroutine

endm

;----[Word]-----------------------------------------------------
CRCC?W macro Win
ERROR You cannot CRC a WORD
endm

;----[Long]-----------------------------------------------------
CRCC?N macro Nin
ERROR You cannot CRC a LONG
endm

;----[Constant]-------------------------------------------------------------
CRCC?C macro Cin
ERROR You cannot CRC a constant
endm

;----[String]---------------------------------------------------------------
CRCC?S macro Cin
ERROR You cannot CRC a String
endm

;----[Label]----------------------------------------------------------------
CRCC?L macro Cin
ERROR You cannot CRC a Label
endm

;----[Bit]------------------------------------------------------------------
CRCC?T macro Regin, Bitin
ERROR CRCing a BIT is not supported
endm

ENDASM

over_BEGIN:

[richard]

Improvements

THIS SEEMS TO WORK
BUT IT WOULD BE NICE TO CRC a WORD,STRING,OR AN ARRAY
PLUS OPTIONALLY RESET CRC TO 0
AND TO USE ANY BANK FOR THE TEMPORY VARS

;CODE STARTS HERE

GOTO over_BEGIN

USERCOMMAND "CRCC" ; Create a command called CRCC
' CRC VAR BYTE SYSTEM 'CRC THIS VAR NEEDS TO BE CREATED IN YOUR CODE

TempD VAR BYTE bank0
TempBC VAR BYTE bank0
TempTMPS var byte bank0
;----[Main Code - Called by the macros]-------------------------------------
asm
_CRCa
MOVLW 8
MOVWF _TempBC
YY MOVF _TempD,W
MOVWF _TempTMPS
MOVF CRC,W
XORWF _TempTMPS,F
RRF _TempTMPS,F
BTFSS STATUS,C
GOTO XX
MOVLW 0X18
XORWF CRC,F
XX RRF CRC,F
RRF _TempD,F
DECFSZ _TempBC,F
GOTO YY
RETURN
;----[crc a Byte]-----------------------------------------------------
CRCC?B macro Bin
MOVE?BB Bin, _TempD ; copy user var to TempVar
L?CALL _CRCa ; run the crc subroutine

endm

;----[Word]-----------------------------------------------------
CRCC?W macro Win
ERROR You cannot CRC a WORD
endm

;----[Long]-----------------------------------------------------
CRCC?N macro Nin
ERROR You cannot CRC a LONG
endm

;----[Constant]-------------------------------------------------------------
CRCC?C macro Cin
ERROR You cannot CRC a constant
endm

;----[String]---------------------------------------------------------------
CRCC?S macro Cin
ERROR You cannot CRC a String
endm

;----[Label]----------------------------------------------------------------
CRCC?L macro Cin
ERROR You cannot CRC a Label
endm

;----[Bit]------------------------------------------------------------------
CRCC?T macro Regin, Bitin
ERROR CRCing a BIT is not supported
endm

ENDASM

over_BEGIN:

[Darrel Taylor]

That's a good start Richard.

>> BUT IT WOULD BE NICE TO CRC a WORD,STRING,OR AN ARRAY
A WORD is simply 2 BYTEs, so you can call the routine twice.

    MOVE?BB Win, _TempD     ; copy lowbyte to TempVar
    L?CALL _CRCa            ; run the crc subroutine
    MOVE?BB Win + 1, _TempD ; copy highbyte to TempVar
    L?CALL _CRCa            ; run the crc subroutine

A LONG has 4 bytes and would need 4 calls.

STRINGs are fixed at compile time and would always give the same result, so CRCing a string wouldn't be very useful.

For an Array, you would need to use a loop to cycle through each byte, sending them one at a time to the CRC routine.

------------
As for the BANKing, you have to manage that yourself when writing in assembly language.
If you write the routine in BASIC, then PBP will handle all the banking issues.

[richard]

usercommand options

thanks for your reply darrel, i have some more quetsions about user commands
can you pass more than one var to a user command ?
can you pass optional var/s to a user command ?
i would need this to pass the array length to my crc command or must i use some other mechanism.

[Darrel Taylor]

Yes, you can pass more than 1 parameter.
For each additional parameter, another letter is added to the macro name.

If you used this line in your program ...
CRCC MyArray, 10

It would call the CRCC?BC macro.

I'm not sure what you mean by "Optional Parameters".
If a macro exists for the number of parameters used, it will call that macro.
So you can have commands that can accept any number of parameters, it just gets very complicated with too many of them.

A command with 1 parameter takes 7 macros, 1 for each type.
A command with 2 parameters takes 7*7=49 macros.
3 parameters ... 7*7*7=343 macros.