This page (revision-48) was last changed on 03-Feb-2023 15:21 by Stefan Haubenthal 

This page was created on 04-Dec-2010 12:59 by Carsten Strotmann

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Version Date Modified Size Author Changes ... Change note
48 03-Feb-2023 15:21 163 bytes Stefan Haubenthal to previous typo
47 01-Jan-2021 10:29 164 bytes Carsten Strotmann to previous | to last
46 14-Dec-2014 21:43 35 KB Carsten Strotmann to previous | to last
45 14-Dec-2014 21:42 35 KB Carsten Strotmann to previous | to last
44 01-Nov-2014 17:28 35 KB Carsten Strotmann to previous | to last
43 01-Nov-2014 17:23 35 KB Carsten Strotmann to previous | to last
42 01-Nov-2014 17:22 35 KB Carsten Strotmann to previous | to last Results VCFB 2014
41 22-Sep-2014 19:43 33 KB Carsten Strotmann to previous | to last

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At line 172 added 80 lines
!!simple 6502 emulator
{{{
\ A simple 6502 emulattion benchmark cas
\ only 11 opcodes are implemented. The memory layout is:
\ 2kB RAM at 0000-07FF, mirrored throughout 0800-7FFF
\ 16kB ROM at 8000-BFFF, mirrored at C000
decimal
create ram 2048 allot : >ram $7FF and ram + ;
create rom 16384 allot : >rom $3FFF and rom + ;
\ 6502 registers
variable reg-a variable reg-x variable reg-y
variable reg-s variable reg-pc : reg-pc+ reg-pc +! ;
\ 6502 flags
variable flag-c variable flag-n variable cycle
variable flag-z variable flag-v : cycle+ cycle +! ;
hex
: w@ dup c@ swap 1+ c@ 100 * or ;
: cs@ c@ dup 80 and if 100 - then ;
: read-byte ( address -- )
dup 8000 < if >ram c@ else >rom c@ then ;
: read-word ( address -- )
dup 8000 < if >ram w@ else >rom w@ then ;
: dojmp ( JMP aaaa )
reg-pc @ >rom w@ reg-pc ! 3 cycle+ ;
: dolda ( LDA aa )
reg-pc @ >rom c@ ram + c@ dup dup reg-a !
flag-z ! 80 and flag-n ! 1 reg-pc+ 3 cycle+ ;
: dosta ( STA aa )
reg-a @ reg-pc @ >rom c@ ram + c! 1 reg-pc+ 3 cycle+ ;
: dobeq ( BEQ <aa )
flag-z @ 0= if reg-pc @ >rom cs@ 1+ reg-pc+ else 1 reg-pc+ then 3 cycle+ ;
: doldai ( LDA #aa )
reg-pc @ >rom c@ dup dup reg-a ! flag-z ! 80 and flag-n !
1 reg-pc+ 2 cycle+ ;
: dodex ( DEX )
reg-x @ 1- FF and dup dup reg-x ! flag-z ! 80 and flag-n !
2 cycle+ ;
: dodey ( DEY )
reg-y @ 1- ff and dup dup reg-y ! flag-z ! 80 and flag-n !
2 cycle+ ;
: doinc ( INC aa )
reg-pc @ >rom c@ ram + dup c@ 1+ FF and dup -rot swap c! dup
flag-z ! 80 and flag-n ! 1 reg-pc+ 3 cycle+ ;
: doldy ( LDY aa )
reg-pc @ >rom c@ dup dup reg-y ! flag-z ! 80 and flag-n !
1 reg-pc+ 2 cycle+ ;
: doldx ( LDX #aa )
reg-pc @ >rom c@ dup dup reg-x ! flag-z ! 80 and flag-n !
1 reg-pc+ 2 cycle+ ;
: dobne ( BNE <aa )
flag-z @ if reg-pc @ >rom cs@ 1+ reg-pc+ else 1 reg-pc+ then
3 cycle+ ;
: 6502emu ( cycles -- )
begin cycle @ over < while
reg-pc @ >rom c@ 1 reg-pc+
dup 4C = if dojmp then dup A5 = if dolda then
dup 85 = if dosta then dup F0 = if dobeq then
dup D0 = if dobne then dup A9 = if doldai then
dup CA = if dodex then dup 88 = if dodey then
dup E6 = if doinc then dup A0 = if doldy then
A2 = if doldx then repeat drop ;
create testcode
A9 c, 00 c, \ start: LDA #0
85 c, 08 c, \ STA 08
A2 c, 0A c, \ LDX #10
A0 c, 0A c, \ loop1: LDY #10
E6 c, 08 c, \ loop2: INC 08
88 c, \ DEY
D0 c, FB c, \ BNE loop2
CA c, \ DEX
D0 c, F6 c, \ BNE loop1
4C c, 00 c, 80 C, \ JMP start
: init-vm 13 0 do i testcode + c@ i rom + c! loop
0 cycle ! 8000 reg-pc ! ;
: bench6502 init-vm &6502 6502emu ;
}}}
This page (revision-48) was last changed on 03-Feb-2023 15:21 by Stefan Haubenthal  Top