Product specifications

SETupINT: LD A,0C5H ;Send CTC bytes to CTC chip to
;’wake’ it up and prepare CTC
OUT (CTC),A ;chip prior to beginning execution of
;VDP interrupts
LD A,1
OUT (CTC),A
IN A,(VDPRGO) ;Clear VDP interrupt flag held in VDP
;read only register on port 2
EI ;Enable new interrupt system
RETI ;Return to calling routine and exit from
;interrupt set up routine.
Part 4
Complete source listing
;
;VARIABLES SECTION
;
CTC EQU 8
VDPRGO EQU 2
;
;TABLES SECTION
;
IJTABLE: 0,0,0,0,0,0,0,0 ;THIS TABLE MUST BE LOCATED
;ON AN 8 BYTE BOUNDARY
;In this case address £8180
;
;VDP INTERRUPTS
;
KILLcTc: LD B,2 ;Shuts off all CTC channels
LD A,3
KILLloop: OUT (CTC),A
OUT (CTC+1),A
OUT (CTC+2),A
OUT (CTC+3),A
DJNZ KILLloop
;
SETupCTC: DI
IM 2
LD A,$81
LD I,A
LD A,£80
OUT (CTC),A
LD HLVDPout
LD (IJtable),HL
;
SETupINT: LD A,0C5H
OUT (CTC),A
LD A,1
OUT (CTC),A
IN A,(VDPRGO)
EI