Posted By
fredrik
on 2020-11-12
04:27:19
|  Re: Looking for collaborator
That's interesting.
I keep getting CPU jams if I skip SEI before storing into $ff3f.
And I can see that the Basic routines to read from RAM do SEI:
.C:0479 78 SEI
.C:047a 8D 3F FF STA $FF3F
.C:047d A0 00 LDY #$00
.C:047f B1 3B LDA ($3B),Y
.C:0481 8D 3E FF STA $FF3E
.C:0484 58 CLI
.C:0485 C9 3A CMP #$3A
.C:0487 B0 0A BCS $0493
.C:0489 C9 20 CMP #$20
.C:048b F0 E6 BEQ $0473
.C:048d 38 SEC
.C:048e E9 30 SBC #$30
.C:0490 38 SEC
.C:0491 E9 D0 SBC #$D0
.C:0493 60 RTS
.C:0494 8D 9C 04 STA $049C
.C:0497 78 SEI
.C:0498 8D 3F FF STA $FF3F
.C:049b B1 00 LDA ($00),Y
.C:049d 8D 3E FF STA $FF3E
.C:04a0 58 CLI
.C:04a1 60 RTS
But this is in fact not necessary at all? Or do I misunderstand something here?
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