Routines
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FDA3: initialise SID, CIA and IRQ
Used by the routines at FCE2, FE66 and FF84.
FDA3 A9 7F LDA #$7F disable all interrupts
FDA5 8D 0D DC STA $DC0D save VIA 1 ICR
FDA8 8D 0D DD STA $DD0D save VIA 2 ICR
FDAB 8D 00 DC STA $DC00 save VIA 1 DRA, keyboard column drive
FDAE A9 08 LDA #$08 set timer single shot
FDB0 8D 0E DC STA $DC0E save VIA 1 CRA
FDB3 8D 0E DD STA $DD0E save VIA 2 CRA
FDB6 8D 0F DC STA $DC0F save VIA 1 CRB
FDB9 8D 0F DD STA $DD0F save VIA 2 CRB
FDBC A2 00 LDX #$00 set all inputs
FDBE 8E 03 DC STX $DC03 save VIA 1 DDRB, keyboard row
FDC1 8E 03 DD STX $DD03 save VIA 2 DDRB, RS232 port
FDC4 8E 18 D4 STX $D418 clear the volume and filter select register
FDC7 CA DEX set X = $FF
FDC8 8E 02 DC STX $DC02 save VIA 1 DDRA, keyboard column
FDCB A9 07 LDA #$07 DATA out high, CLK out high, ATN out high, RE232 Tx DATA high, video address 15 = 1, video address 14 = 1
FDCD 8D 00 DD STA $DD00 save VIA 2 DRA, serial port and video address
FDD0 A9 3F LDA #$3F set serial DATA input, serial CLK input
FDD2 8D 02 DD STA $DD02 save VIA 2 DDRA, serial port and video address
FDD5 A9 E7 LDA #$E7 set 1110 0111, motor off, enable I/O, enable KERNAL, enable BASIC
FDD7 85 01 STA $01 save the 6510 I/O port
FDD9 A9 2F LDA #$2F set 0010 1111, 0 = input, 1 = output
FDDB 85 00 STA $00 save the 6510 I/O port direction register
This entry point is used by the routines at FC93 and FF5B.
FDDD AD A6 02 LDA $02A6 get the PAL/NTSC flag
FDE0 F0 0A BEQ $FDEC if NTSC go set NTSC timing
else set PAL timing
FDE2 A9 25 LDA #$25
FDE4 8D 04 DC STA $DC04 save VIA 1 timer A low byte
FDE7 A9 40 LDA #$40
FDE9 4C F3 FD JMP $FDF3
FDEC A9 95 LDA #$95
FDEE 8D 04 DC STA $DC04 save VIA 1 timer A low byte
FDF1 A9 42 LDA #$42
FDF3 8D 05 DC STA $DC05 save VIA 1 timer A high byte
FDF6 4C 6E FF JMP $FF6E
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