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author Vas Crabb <vas@vastheman.com>2019-03-26 11:13:37 +1100
committer Vas Crabb <vas@vastheman.com>2019-03-26 11:13:37 +1100
commit97b67170277437131adf6ed4d60139c172529e4f (patch)
tree7a5cbf608f191075f1612b1af15832c206a3fe2d /src/devices/cpu/m6502/xavix2000.cpp
parentb380514764cf857469bae61c11143a19f79a74c5 (diff)
(nw) Clean up the mess on master
This effectively reverts b380514764cf857469bae61c11143a19f79a74c5 and c24473ddff715ecec2e258a6eb38960cf8c8e98e, restoring the state at 598cd5227223c3b04ca31f0dbc1981256d9ea3ff. Before pushing, please check that what you're about to push is sane. Check your local commit log and ensure there isn't anything out-of-place before pushing to mainline. When things like this happen, it wastes everyone's time. I really don't need this in a week when real work™ is busting my balls and I'm behind where I want to be with preparing for MAME release.
Diffstat (limited to 'src/devices/cpu/m6502/xavix2000.cpp')
-rw-r--r--src/devices/cpu/m6502/xavix2000.cpp101
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();