git.defcon.no Git - z80cpm/blob - tiktok.asm

   1 ; tiktok.asm
   2 ; ASM dialect is for crasm/z80, producing Intel HEX.
   3 ; Compile using "crasm -o tiktok.hex tiktok.asm" and transfer
   4 ; to CP/M system for final conversion to COM file using LOAD.COM
   5 ;
   6 ; A sample program that uses a busy-waiting spinloop
   7 ; to produce 1ms delays. 5*200 iterations of calls to
   8 ; the delay loop is made, to provide a 1sec delay per "Tick".
   9 ; 60 iterations of printint "Tick" to the console is done
  10 ; for a full minute of waiting time.
  11 ; Console output is done using CP/M BDOS call 9 (C_WRITRSTR)
  12
  13 CPU Z80
  14 OUTPUT HEX
  15
  16 ; CP/M constants used
  17 STROUT  EQU 9
  18 BDOS    EQU 5
  19
  20 ; Start COM file at TPA start (Origin 0x100)
  21 * = $100
  22 START           LD DE, STARTMSG
  23                 LD C, STROUT
  24                 CALL BDOS
  25
  26                 LD A, 60
  27 LOOP            PUSH AF
  28
  29                 LD DE, MESSAGE
  30                 LD C, STROUT
  31                 CALL BDOS
  32
  33                 LD B, 5 ; 5 * 200 msec = 1000ms = 1 sec :P
  34 SEC             LD A, 200
  35                 CALL DELAY
  36                 DEC B
  37                 JR NZ, SEC
  38
  39                 POP AF
  40                 DEC A
  41                 JR NZ, LOOP
  42
  43                 LD DE, STOPMSG
  44                 LD C, STROUT
  45                 CALL BDOS
  46
  47                 RET
  48
  49 ; Delay routine, A register contains number of Delay iterations.
  50 ; Does not clobber, but A is reduced to zero on completion
  51 ; Values tried (may be good) for 7.3728MHz: C=13, B=44
  52 DELAY           PUSH BC                 ; Save B and C registers
  53 DLY_START       LD C, 13                ; Coarse factor
  54 DLY_LOOPO       LD B, 44                ; Fine factor
  55 DLY_LOOPI       DJNZ DLY_LOOPI          ; Decrement B until BZero
  56                 DEC C                   ; Decrement C ..
  57                 JR NZ, DLY_LOOPO        ; .. until zero
  58                 DEC A                   ; Do next main iteration
  59                 JR NZ, DLY_START        ; until given numer is zero
  60                 POP BC                  ; Restore B and C registers
  61                 RET                     ; Return from delay.
  62
  63 ; String constants here, to avoid having them clobber $100H
  64 ; Note CP/M BDOS call 9 format, $ is string terminator.
  65 STARTMSG ASC "Timertest\r\n$"
  66 MESSAGE ASC "Tick\r\n$"
  67 STOPMSG ASC "Done\r\n$"