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2019-02-19 15:51

oziphantom

Registered: Oct 2014
Posts: 478

SD2IEC fastloader

Does anybody know of a system that fast loads, or a disassembly of a fast loader that SD2IEC supports?

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2020-02-26 10:50

Krill

Registered: Apr 2002
Posts: 2839

Quoting Krill

Okay, didn't get around cleaning it up yet and not sure if this helps, but this is an example of what i did:
; scratch "TEMP" lda #FLOPPYMW - scratch ldx #<scratch ldy #>scratch jsr $ffbd; SETNAM lda #$6f; secondary address: command/error channel sta $b9 lda #$20; LISTEN jsr sendslow jsr $f3e6; send secondary address and filename lda #$3f; UNLISTEN jsr sendslow jsr $ee03; clear ATN [...] sendslow ora $ba sta $95 lda $dd00 and #%11001111 ora #%00001000 sta $dd00 - bit $dd00 bpl - sei jmp $ed5a; send byte

Meanwhile, it turned out that i forgot the EOI delay (http://unusedino.de/ec64/technical/aay/c64/romeeb3.htm), and it's quite crucial. So "sendslow" becomes:

sendslow ora $ba
         sta $95
         lda $dd00
         and #%11001111
         ora #%00001000
         sta $dd00
-        bit $dd00
         bpl -
         ldx #$b8
-        dex
         bne -
         sei
         jmp $ed5a; send byte

DFLTO ($9a) for LISTEN and DFLTN ($99) for TALK also don't appear to be set, which i do in a clean version in another codebase:

            CLEAR_DATA_OUT_CLEAR_CLK_OUT_ASSERT_ATN
:           SET_FLAGS_N_DATA_V_CLK
            bpl :-
            ldx #$b8; delay
:           dex     ; of
            bne :-  ; ~1 ms
            lda FA
            sta DFLTO
            ora #SA_LISTEN
            sta BSOUR
            sei
            jsr NOEOI; send byte

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