This message is FYI :)
- Corrected some bugs, especially the one that caused NestorBASIC 1.0 to
hang on Panasonic WSX machines.
I assume this was a bug in the MoonBlaster MSX-MUSIC detection routine.
The proper way to detect the MSX-MUSIC is this:
1. First check for internal MSX-MUSIC: Check for APRL on 4018h of the
MSX-MUSIC ROM. If found, MSX-MUSIC was successfully found.
2. Now check for FM-PAC: Check for OPLL on 401Ch of the MSX-MUSIC ROM. If
found: set bit 0 of address 7FF6h. If not found: no FM-PAC inserted.
The bug is caused by MoonBlaster only checking for 'OPLL' and setting bit 0
of address 7FF6h regardless of the MSX-MUSIC was internal or external. On
these Panasonic machines 7FF6h belongs to the internal mapper, causing a crash.
Setting of bit 0 address 7FF6h is required on FM-PAC to enable it to listen
to I/O commands. Without bit 0 of 7FF6h set, FM-PAC only listens to memory
I/O 7FF4h and 7FF5h.
This mechanism has two purposes:
1. to prevent the I/O conflict when an FM-PAC is inserted into machines
with MSX-MUSIC on-board.
2. to enable multiple FM-PACs to be used by accessing their memory I/O
addresses.
So in short: there's no design flaw in the Panasonic machines (which has
been suggested), there's 'just' a bug in the MoonBlaster MSX-MUSIC
detection routine.
Full sourcecode of correct MSX-MUSIC detection and initialisation follows.
Greetings,
Patriek
---
FMSlot: db 0 ; slotnumber of MSX-MUSIC if found.
SearchTemp: db 0 ; temporary variable
InitFM: xor a
ld [FMSlot],a ; reset slotnr
ld b,4
.pri_l: pushbc
ld a,4
sub b
ld c,a
ld hl,EXPTBL
add a,l
ld l,a
ld a,[hl]
add a,a
jr nc,.notExp
ld b,4 ; slot is expanded
.exp_l: pushbc
ld a,24h
sub b
rlca
rlca
or c
ld [SearchTemp],a
call.SearchFM
ld a,[FMSlot]
or a
pop bc
jr nz,.end
djnz.exp_l
.nextpri:
pop bc
djnz.pri_l
ret
.notExp:; slot is not expanded
ld a,c
ld [SearchTemp],a
call.SearchFM
ld a,[FMSlot]
or a
jp z,.nextpri
.end: pop bc
ret
.SearchFM:
ld b,8
ld hl,.TxtAPRL
ld de,4018h
call.Compare
ret nc
ld b,4
ld hl,.TxtOPLL
ld de,401Ch
call.Compare
ret c
ld hl,7FF6h
pushaf
pushhl
callRDSLT
or 1
ld e,a
pop hl
pop af
callWRSLT
or a
ret
.Compare:
ld a,[SearchTemp]
ld c,a
.loop: pushbc
pushhl
pushde
ld a,c
ex de,hl
callRDSLT
pop de
pop hl
pop bc
cp [hl]
scf
ret nz
inc hl
inc de
djnz.loop
ld a,c
ld [FMSlot],a
or a
ret
.TxtAPRL: db APRL
.TxtOPLL: db OPLL
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