From: Baltissen, GJPAA (Ruud) (ruud.baltissen_at_abp.nl)
Date: 2004-09-09 07:46:50

Hallo allemaal,

I posted the source of my 8250 diskcopy program. The question arrised why
this and other programs were so slow. I thought that the reason was that
every byte was sent with the complete circus of ATN, LISTEN etc. I checked
that yesterday and... it isn't. But what puzzles me: I send the bytes in
blocks of 256 bytes. And the last one is received with EOI = True. And that
is what I do not understand. The routine that sends the 256 bytes:

J_0361	ldx	#$06
		jsr	P_FFC9		; $FFC9
		ldy	#$00
		sty	$01

B_036A	sty	$00
		lda	($01),Y
		jsr	P_FFD2		; $FFD2
;		lda	$90
;		bne	B_037C
		ldy	$00
		bne	B_036A
B_037C	jsr	P_FFCC		; $037C , $FFCC

What tells $FFD2 to send the last byte with an acive EOI ????

   / __|__
  / /  |_/     Groetjes, Ruud
  \ \__|_\
   \___|       URL: Ruud.C64.org



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