Bob’s Notebook: Digital Clock for the TS 2068

This bit of code will provide a digital 24-hour clock which can be used in various applications. It uses the Z80’s Interrupt Mode 2 to allow the clock to appear, via multitasking, while another program is operating.

The clock will show hours, minutes and seconds in the upper right corner of the screen. An experienced machine code programmer can alter the screen location, if this is desirable.

To start the clock GO TO 3000, which POKEs the time value entered into the code and then does a RANDOMIZE USR 65020 to activate the IM2 routine and divert the interrupts. GO TO 4000 to stop the clock and disable the clock.

1 REM Bob Mitchell
2 REM Sinc-Link v9 n5
3 REM https://archive.org/details/SincLink/Sinc-Link%20Vol%2009%20No%205/page/27/mode/1up
5 CLEAR 65019
100 REM Clock
105 REM GO TO LINE 3000 to start clock.  Enter time in 24-hour format (eg 7:39pm is 192800)
110 REM GO TO LINE 4000 to stop clock
115 REM value in 65097 can be changes to alter clock speed. 60 is normal; higher value slows clock
120 REM turn clock off before using NMI button
1000 DATA 33,0,252,1,251,0,113,35,16,252,113,62,195,50,251,251
1001 DATA 33,60,254,34,252,251,62,252,237,71,237,94,253,54,2,0
1002 DATA 24,11,22,0,24,48,48,58,48,48,58,48,48,33,30,254
1003 DATA 6,11,126,215,35,5,32,250,201,237,86,62,63,237,71,201
1004 DATA 245,229,197,213,175,58,1,255,60,50,1,255,254,60,218,74
1005 DATA 0,175,50,1,255,58,9,255,60,50,9,255,254,10,56,104
1006 DATA 175,50,9,255,58,8,255,60,50,8,255,254,6,56,89,175
1007 DATA 50,8,255,58,6,255,60,50,6,255,254,10,56,74,175,50
1008 DATA 6,255,58,5,255,60,50,5,255,254,6,56,59,175,50,5
1009 DATA 255,58,3,255,60,50,3,255,254,4,40,2,32,21,58,2
1010 DATA 255,254,2,32,14,58,3,255,175,50,3,255,58,2,255,175
1011 DATA 50,2,255,58,3,255,50,3,255,254,10,56,11,175,50,3
1012 DATA 255,58,2,255,60,50,2,255,62,24,50,10,255,62,2,50
1013 DATA 11,255,79,6,255,10,135,135,135,79,6,0,33,128,61,9
1014 DATA 58,10,255,95,62,64,87,6,8,126,18,35,20,5,32,249
1015 DATA 58,10,255,60,50,10,255,58,11,255,60,254,10,40,2,24
1016 DATA 206,195,74,0,0,0,0,0,10,0,0,10,0,0,0,0
3000 RESTORE 1000: FOR i=1 to 272: READ a: POKE 65019+i,a: NEXT i
3005 INPUT "time? hhmmss "; LINE t$: POKE 65281,0: POKE 65282,VAL t$(1): POKE 65283, VAL t$(2)
3010 POKE 65285,VAL t$(3): POKE 65286, VAL t$(4)
3020 POKE 65288,VAL t$(5):POKE 65289,VAL t$(6)
3030 RANDOMIZE USR 65020: STOP: REM start clock
4000 RANDOMIZE USR 65077: STOP: REM stop clock
9000 REM SAVE CLOCK