mirror of
https://github.com/TomHarte/CLK.git
synced 2024-12-29 13:29:46 +00:00
148 lines
3.7 KiB
Plaintext
148 lines
3.7 KiB
Plaintext
65816 behavior on VICE and true hardware
|
|
========================================
|
|
|
|
Johann Klasek, j AT klasek at
|
|
2017-12-02
|
|
|
|
|
|
Testenvironment:
|
|
|
|
Hardware:
|
|
Tested on LTC64, a turbo card for the Commodore 64
|
|
in-place of CPU 6510 (which moves to the card)
|
|
with a WDC's 65C816, 32 KByte ROM and 256 KByte RAM.
|
|
based on magazine article c't "C64 aufgemotzt", 1987/06 p. 94
|
|
http://klasek.at/c64/ltc64 (german)
|
|
Redesigned and implemented by Christoph Egretzberger
|
|
and software integration by Johann Klasek
|
|
|
|
Software:
|
|
Jamaica Monitor (Jammon) 4.1, native '816
|
|
C64 ROMs (Kernal+BASIC)
|
|
|
|
---------------------------------------------------------------------
|
|
Case 1: Wrap-around for addressing mode "absolute"
|
|
for opcodes TSB, TRB, STX, STY, LDX, LDY
|
|
|
|
VICE WDC
|
|
!e
|
|
a 1000 clc
|
|
xce native mode
|
|
rep #$30 16-bit for X/Y and A/M
|
|
lda #$0404 Data Bank Register register
|
|
pha akku in 16 bit
|
|
plb pull DBR twice
|
|
plb
|
|
lda #$7777 no-wrap marker
|
|
sta $050000 to bank 5
|
|
sta $058887
|
|
lda #$5555 unchanged marker
|
|
sta $048887 into bank 4
|
|
ldy #$8888 change marker
|
|
tyx now in X and Y
|
|
sty $ffff high byte of Y is where?
|
|
ldy $ffff,x Y=5555 Y=7777 value for Y comes from which bank?
|
|
sty $0002 save as intermediate result, because we do more
|
|
lda $ffff A=7788 A=8888 fetch, does no wrap even on VICE
|
|
ldx $0000 X=2088 X=20b5 see if wrapping occured (from sty above)
|
|
eor #$ffff A=8877 A=7777 invert akku, 2nd part ...
|
|
trb $ffff M=0088 M=8888 reset bits (which are already cleared)
|
|
tsb $ffff M=88ff M=ffff set these bits giving a $ffff value
|
|
ldy $ffff Y=88ff Y=ffff back to ldy test
|
|
brk
|
|
|
|
!d Jammon alternate display mode
|
|
d disassemble on current PC
|
|
m 04ffff show memory including 050000
|
|
m 040000 start of bank 4 (wrap around area),
|
|
and intermediate result in 040002
|
|
m 048887 X indexed wrap area
|
|
m 058887 X indexed no wrap area
|
|
z 1000 start single-stepping
|
|
z single step until BRK or ...
|
|
g go to BRK
|
|
|
|
Results VICE WDC
|
|
|
|
$050001 $77 $77 marker, never changed
|
|
$050000 $77 $ff modified by TRB/TSB
|
|
$04ffff $ff $ff modified by TRB/TSB
|
|
$040003 $55 $77 read value (low) from LDY $FFFF,X
|
|
$040002 $55 $77 read value (high) from LDY $FFFF,X
|
|
read value
|
|
$040000 $88 ?? (if no wrapping for STY $FFFF, TRB/TSB $FFFF)
|
|
only changed if wrapping
|
|
$058888 $77 $77 marker, never changed
|
|
$058887 $77 $77 marker, never changed
|
|
$048888 $55 $55 marker, never changed
|
|
$048887 $55 $55 marker, never changed
|
|
|
|
A: $8877 $7777 value from $04ffff/$050000 after STY $FFFF
|
|
X: $??88 $???? value from $040000/$040001 with high byte of Y
|
|
in low byte of X after STY $FFFF
|
|
Y: $88ff $ffff value from TRB/TSB $FFFF
|
|
|
|
|
|
|
|
---------------------------------------------------------------------
|
|
Case 2: Wrap-around for Direct Page Indexed Addressing
|
|
in Emulation Mode
|
|
|
|
### Variant 1
|
|
|
|
r
|
|
# set M X E to "1"
|
|
e
|
|
# set DBR to 00
|
|
|
|
a 1000 sec
|
|
xce emulation mode
|
|
lda #$20 set highbyte
|
|
xba
|
|
lda #$00 lowbyte 16-bit akku
|
|
tcd direct page address to $2000
|
|
ldx #$20 index
|
|
lda #$88 marker for wrap
|
|
sta $2010
|
|
lda #$77 marker for no-wrap
|
|
sta $2110
|
|
lda $f0,x which marker?
|
|
stz $f0,x write (non-6502)
|
|
brk
|
|
|
|
!d Jammon alternate display mode
|
|
d disassemble on PC
|
|
m 2010 show wrap area
|
|
m 2110 show no-wrap area
|
|
z 1000 start single-stepping
|
|
z single step until BRK or ...
|
|
g go to BRK
|
|
|
|
Results VICE WDC
|
|
|
|
$2010 00 00 wrap area: =00 from STZ
|
|
$2110 77 77 no-wrap area
|
|
|
|
A: $2088 $2088 A low: 88 = wrap, 77 = no-wrap
|
|
|
|
|
|
### Variant 2
|
|
|
|
Based on variant 1:
|
|
|
|
a 1005 lda #$01 direct page not aligned!
|
|
tcd direct page at $2001
|
|
ldx #$1f correction to hit the
|
|
same memory locations
|
|
for monitoring
|
|
|
|
g 1000
|
|
|
|
Results VICE WDC
|
|
|
|
$2011 88 88 wrap area: =00 from STZ
|
|
$2111 00 00 no-wrap area
|
|
|
|
A: $2077 $2077 A low: 88 = wrap, 77 = no-wrap
|
|
|