If you need to do some simple time delays (approximately 8 to 18000+ cycles), this Delay Macro can be used by low-power PICs (like the pic10, pic12, pic16) which have a shallow call stack of 2 levels for routines such as long delays. An example using this sort of delay is shown in RS232 PIC Software USART code example.
The timing granularity of this delay macro is about 3 cycles, but it can be refined to 1 cycle accuracy if you wish to improve this macro further. Additional improvements can be made by putting the main loop into a call routine to save on program-code space (saving yourself a few program codes each time the macro is used).
You can download DelayM Macro, or you can copy and paste the code shown below into your ASM code editor.
;*************************************************************** ;Delay Macro ;Wait approximately delCntVar cycles. ~ 1998oct - by J Da Silva ;enter: delCntVar=number of cycles to wait ;exit : ;ram : DlyCnt[0,1] ; DelayM macro delCntVar local DelayLp local majCnt local minCnt variable majCnt = 1 variable minCnt = delCntVar - 8 if minCnt < 771 movlw (delCntVar-2)/3+1 movwf DlyCnt DelayLp decfsz DlyCnt,f goto DelayLp else while minCnt > 768 minCnt -= 771 majCnt += 1 endw movlw majCnt movwf DlyCnt movlw minCnt/3+1 movwf DlyCnt+1 DelayLp decfsz DlyCnt+1,f goto DelayLp decfsz DlyCnt,f goto DelayLp endif endm ;--------------------------------------------------------------- DlyCnt res 2 ;delay wait counter (2 bytes) |
If you find this macro useful, I will appreciate a little credit for providing it here for your use/project (for example, in your source code comments, or even a web link back to this web page is great if you have a project that uses it that you want to show/demonstrate). Thanks.
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