diff options
Diffstat (limited to 'src/devices/cpu/m6502/xavix2000.cpp')
-rw-r--r-- | src/devices/cpu/m6502/xavix2000.cpp | 101 |
1 files changed, 25 insertions, 76 deletions
diff --git a/src/devices/cpu/m6502/xavix2000.cpp b/src/devices/cpu/m6502/xavix2000.cpp index 0c928ce159d..94b56308e0d 100644 --- a/src/devices/cpu/m6502/xavix2000.cpp +++ b/src/devices/cpu/m6502/xavix2000.cpp @@ -7,8 +7,8 @@ The dies for these are marked SSD 2000 NEC 85605-621 - and possibly - SSD 2002 NEC 85054-611 (although this might use even more opcodes and need it's own file) + + SSD 2002 NEC 85054-611 6502 with custom opcodes integrated gfx / sound @@ -17,77 +17,12 @@ see xavix.cpp for basic notes - the machines using the '2000' series chips seem to have more extra - opcodes, so presumably these were only available in those models. - of note, push x / push y and pull x / pull y - - Dirt Rebel MX, which is confirmed as 2000 type however seems to require - some of the documented but 'undocumented' opcodes on the 6502 to have additonal - meaning for one specific function on startup - - this just seems to be some very buggy checksum code where the games don't even care about the result... - (actually it looks like some games might be using it as a PRNG seed?) - - a is 80 when entering here? - - 01BC37: A0 3F ldy #$3f - 01BC39: B2 clr a // clear acculuator - 01BC3A: 1B spa0 a // store 'accumulator' into byte 0 of PA 'address' register - 01BC3B: 9B spa2 a // store 'accumulator' into byte 2 of PA 'address' register - - -- loop point 2 - 01BC3C: 98 tya // y -> a (3f on first run of loop) - 01BC3D: 5B spa1 a // store 'accumulator' into byte 1 of PA 'address' register (003f00 on first loop?) - - -- loop point 1 - 01BC3E: A3 ldal0 a // read byte 0 of 32-bit 'long' register into accumulator - 01BC3F: 73 adcpa // adc ($Address PA) - 01BC40: 83 stal0 a // store accumulator back in byte 0 of 32-bit 'long' register (even byte checksum?) - 01BC41: FB incpa // increase 'address' register PA - 01BC42: A7 ldal1 a // read byte 1 of 32-bit 'long' register into accumulator - 01BC43: 73 adcpa // adc ($Address PA) - 01BC44: 87 stal1 a // store accumulator back in byte 0 of 32-bit 'long' register (odd byte checksum?) - 01BC45: FB incpa // increase 'address' register PA - 01BC46: D0 F6 bne $1bc3e // (branch based on PA increase, so PA must set flags?, probably overflows after 0xffff if upper byte is 'bank'? or at 0xff if this really is a mirror of the function below - - 01BC48: 88 dey // decrease y, which contained 3f at the start - 01BC49: 10 F1 bpl $1bc3c // branch back to loop point 2 to reload counter - - // contains the odd byte checksum once we drop out the loop - 01BC4B: 8D FB 00 sta $00fb // store it in zero page memory - 01BC4E: A3 ldal0 a // get the even byte checksum from byte 0 of 32-bit 'long' register - 01BC4F: 8D FA 00 sta $00fa // store it in zero page memory - 01BC52: 07 oral1 a // why do we want to do this? (routine below does it too) - 01BC53: D0 03 bne $1bc58 - 01BC55: CE FA 00 dec $00fa - 01BC58: 80 retf - - this is presumably meant to be similar to the function found in Namco - Nostalgia 2 - - // A is 80 on entry - 09FFD8: A9 3F lda #$3f - 09FFDA: 85 01 sta $01 // set upper bit of pointer at 0x0000 to 3f (it completely fails to initialize the ram at 00, we currently init it to ff, but should probably be 0?) - 09FFDC: A0 00 ldy #$00 // clear inner loop counter - -- loop point 1 and 2 - 09FFDE: AD FA 00 lda $00fa // read current even byte checksum value from zero page ram fa (game also completely fails to initialize this) - 09FFE1: 71 00 adc ($00), y // so 3f00 + y first outer loop, 3e00 + y second outer loop with y increasing in inner loop (add byte read to even checksum byte?) - 09FFE3: 8D FA 00 sta $00fa // store even checksum at 0xfa in zero page ram - 09FFE6: C8 iny // increase counter y - 09FFE7: AD FB 00 lda $00fb // read current odd byte checksum value from zero page ram fb (likewise never initialized!) - 09FFEA: 71 00 adc ($00), y // 3f00 + y (add byte read to odd checksum byte) - 09FFEC: 8D FB 00 sta $00fb // store odd checksum byte at 0xfb in zero page ram - 09FFEF: C8 iny // increase y - 09FFF0: D0 EC bne $9ffde // branch back if y hasn't overflowed (so work on 0x100 bytes, looping back 0x7f times) - 09FFF2: C6 01 dec $01 // decrease accumulator (started at 3f) (inner loop counter already 0 because it overflowed) - 09FFF4: 10 E8 bpl $9ffde // branch back - - // checksums are already in place after loop so no need to copy them like in above - 09FFF6: 0D FA 00 ora $00fa // same weird 'or' call - -- - 09FFF9: D0 03 bne $9fffe - 09FFFB: CE FA 00 dec $00fa - 09FFFE: 80 retf + the 2000 chip has more opcodes than the 97/98 chips in xavix.cpp, and + is a similar die structure to the 2002 chip, but doesn't seem to have any + additional capabilities. + + the 2002 chip seems to be the one that was officially dubbed 'SuperXaviX' + and has additional video capabilities on top of the extended opcodes. ***************************************************************************/ @@ -96,10 +31,13 @@ #include "xavix2000.h" #include "xavix2000d.h" -DEFINE_DEVICE_TYPE(XAVIX2000, xavix2000_device, "xavix2000", "XaviX (SSD 2000 / 2002)") +DEFINE_DEVICE_TYPE(XAVIX2000, xavix2000_device, "xavix2000", "XaviX (SSD 2000)") +DEFINE_DEVICE_TYPE(XAVIX2002, xavix2002_device, "xavix2002", "XaviX (SSD 2002) (SuperXaviX)") -xavix2000_device::xavix2000_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock) : - xavix_device(mconfig, XAVIX2000, tag, owner, clock) + + +xavix2000_device::xavix2000_device(const machine_config &mconfig, device_type type, const char *tag, device_t *owner, uint32_t clock) : + xavix_device(mconfig, type, tag, owner, clock) { program_config.m_addr_width = 24; program_config.m_logaddr_width = 24; @@ -107,6 +45,17 @@ xavix2000_device::xavix2000_device(const machine_config &mconfig, const char *ta sprogram_config.m_logaddr_width = 24; } +xavix2000_device::xavix2000_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock) : + xavix2000_device(mconfig, XAVIX2000, tag, owner, clock) +{ +} + +xavix2002_device::xavix2002_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock) : + xavix2000_device(mconfig, XAVIX2002, tag, owner, clock) +{ +} + + void xavix2000_device::device_start() { xavix_device::device_start(); |