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148 lines
3.7 KiB
Plaintext
148 lines
3.7 KiB
Plaintext
65816 behavior on VICE and true hardware
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========================================
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Johann Klasek, j AT klasek at
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2017-12-02
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Testenvironment:
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Hardware:
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Tested on LTC64, a turbo card for the Commodore 64
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in-place of CPU 6510 (which moves to the card)
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with a WDC's 65C816, 32 KByte ROM and 256 KByte RAM.
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based on magazine article c't "C64 aufgemotzt", 1987/06 p. 94
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http://klasek.at/c64/ltc64 (german)
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Redesigned and implemented by Christoph Egretzberger
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and software integration by Johann Klasek
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Software:
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Jamaica Monitor (Jammon) 4.1, native '816
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C64 ROMs (Kernal+BASIC)
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---------------------------------------------------------------------
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Case 1: Wrap-around for addressing mode "absolute"
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for opcodes TSB, TRB, STX, STY, LDX, LDY
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VICE WDC
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!e
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a 1000 clc
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xce native mode
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rep #$30 16-bit for X/Y and A/M
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lda #$0404 Data Bank Register register
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pha akku in 16 bit
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plb pull DBR twice
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plb
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lda #$7777 no-wrap marker
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sta $050000 to bank 5
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sta $058887
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lda #$5555 unchanged marker
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sta $048887 into bank 4
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ldy #$8888 change marker
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tyx now in X and Y
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sty $ffff high byte of Y is where?
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ldy $ffff,x Y=5555 Y=7777 value for Y comes from which bank?
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sty $0002 save as intermediate result, because we do more
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lda $ffff A=7788 A=8888 fetch, does no wrap even on VICE
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ldx $0000 X=2088 X=20b5 see if wrapping occured (from sty above)
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eor #$ffff A=8877 A=7777 invert akku, 2nd part ...
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trb $ffff M=0088 M=8888 reset bits (which are already cleared)
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tsb $ffff M=88ff M=ffff set these bits giving a $ffff value
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ldy $ffff Y=88ff Y=ffff back to ldy test
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brk
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!d Jammon alternate display mode
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d disassemble on current PC
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m 04ffff show memory including 050000
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m 040000 start of bank 4 (wrap around area),
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and intermediate result in 040002
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m 048887 X indexed wrap area
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m 058887 X indexed no wrap area
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z 1000 start single-stepping
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z single step until BRK or ...
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g go to BRK
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Results VICE WDC
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$050001 $77 $77 marker, never changed
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$050000 $77 $ff modified by TRB/TSB
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$04ffff $ff $ff modified by TRB/TSB
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$040003 $55 $77 read value (low) from LDY $FFFF,X
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$040002 $55 $77 read value (high) from LDY $FFFF,X
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read value
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$040000 $88 ?? (if no wrapping for STY $FFFF, TRB/TSB $FFFF)
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only changed if wrapping
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$058888 $77 $77 marker, never changed
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$058887 $77 $77 marker, never changed
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$048888 $55 $55 marker, never changed
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$048887 $55 $55 marker, never changed
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A: $8877 $7777 value from $04ffff/$050000 after STY $FFFF
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X: $??88 $???? value from $040000/$040001 with high byte of Y
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in low byte of X after STY $FFFF
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Y: $88ff $ffff value from TRB/TSB $FFFF
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---------------------------------------------------------------------
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Case 2: Wrap-around for Direct Page Indexed Addressing
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in Emulation Mode
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### Variant 1
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r
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# set M X E to "1"
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e
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# set DBR to 00
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a 1000 sec
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xce emulation mode
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lda #$20 set highbyte
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xba
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lda #$00 lowbyte 16-bit akku
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tcd direct page address to $2000
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ldx #$20 index
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lda #$88 marker for wrap
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sta $2010
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lda #$77 marker for no-wrap
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sta $2110
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lda $f0,x which marker?
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stz $f0,x write (non-6502)
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brk
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!d Jammon alternate display mode
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d disassemble on PC
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m 2010 show wrap area
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m 2110 show no-wrap area
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z 1000 start single-stepping
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z single step until BRK or ...
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g go to BRK
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Results VICE WDC
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$2010 00 00 wrap area: =00 from STZ
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$2110 77 77 no-wrap area
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A: $2088 $2088 A low: 88 = wrap, 77 = no-wrap
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### Variant 2
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Based on variant 1:
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a 1005 lda #$01 direct page not aligned!
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tcd direct page at $2001
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ldx #$1f correction to hit the
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same memory locations
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for monitoring
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g 1000
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Results VICE WDC
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$2011 88 88 wrap area: =00 from STZ
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$2111 00 00 no-wrap area
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A: $2077 $2077 A low: 88 = wrap, 77 = no-wrap
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