delay.asm

来自「胎压监测系统接收端控制器motorolar开发源代码」· 汇编 代码 · 共 23 行

* Delay.asm

**********************************************************************
* Delay                                                              *
* Simple delay routine. Delay time is equal to:                      *
* (7+3)+(256*5*XR)+(XR*3)+4                                          *
* bus cycles, or 1283*XR + 14.                                       *
* If the bus frequency is 1.2288MHz, this is equal to just over      *
* 1 ms per XR bit.                                                   *
*                                                                    *
* INPUT: Cycle count in XR                                           *
* Usage example:                                                     *
*               LDX     #DELAY                                       *
*               JSR     Delay                                        *
**********************************************************************
                                                        ;7 bus cycles to get here
Delay:          CLR     BUFFER                          ;3 bus cycles

LoopX:          DBNZ    BUFFER,LoopX                    ;5 bus cycles
                DBNZX   LoopX                           ;3 bus cycles

Finished:       RTS                                     ;4 bus cycles