HD6301V1
8bit Hitachi microcontroller used for multiplayer communication in cartridges like League Bowling.
Compatible with the Motorola 6803 but has additionnal instructions.
Clocked at 1MHz using the 4MB signal (divided by 4 internally).
Datasheet
Official datasheet: [[1]]
Code
The HD6301 has an internal 4KB ROM section holding program data.
A dump is available, coming from a prototype Riding Hero cart: File:HD6301.zip (2x overdump) - Credits to NeoTurfMasta
Commented source code (still some work left...):
;Vectors:
;TRAP: F4D6 (error)
;SC1: F4BA (link receive)
;TOF: F4D6 (error)
;OCF: F4D6 (error)
;ICF: F4D6 (error)
;IRQ1: F4CB (CPU write)
;SWI: F4D6 (error)
;NMI: F4D6 (error)
;RESET: F000 (start)
;RAM:
;$C2 start of message buffer (14 bytes ?)
;$D0~$D1
;$D2~$D3
;$D4~$D5
;$D6~$D7
;$D8~$D9
;$DA~$DB
;$DC
;$E2 is an error counter ?
;$E3 some counter ? -----------------
;$E4 some bitmask ? -----------------
;$E5 is receive byte counter
;$E6 ?
;$E7 is the output code (read by CPU)
;$E8 related to $F3 ?
;$E9 is the input code (wrote by CPU)
;$EA another byte counter ?
;$EB bit 0 is CPU write flag ? (data ready in $E9), bit 1 is link receive flag
;$EC is TRCS register copy
;$ED is the received code (link)
;$EE~$EF buffer (FIFO ?) pointer
;$F0 receive timeout timer
;$F1 is status code/port1 mirror
;$F2 some bitmask ? -----------------
;$F3 is lower nibble of input code (parameter ?)
;$F4 start of some short buffer ?
;Status bit 0 (D8) is command error (D,E,F: wrong command)
;Status bit 2 (D10) is overrun receive error
org $F000
; RESET
LF000:
sei
lds #$00FF ; Clear RAM
ldx #$0080
LF007:
clr $7F,x
dex
bne LF007
ldaa #$40 ; Enable RAM (lol)
staa X0014
ldaa #$04 ; 62500bps internal clock
staa X0010
ldaa #$1A ; RIE, RXE, TXE
staa X0011
ldaa #$48 ; Port3 IS3/IRQ1 enable, latch enable
staa X000F
ldaa X0011 ; Clear TRCS flags
ldaa X0012 ; Receive register
ldaa #$F1 ; Port1 direction 11110001
staa X0000
ldaa #$00 ; Port1 data
staa X0002
ldaa #$00 ; Port3 direction (inputs)
staa X0004
ldaa #$FF ; Port4 direction (outputs)
staa X0005
ldaa X0006 ; Clear port3 latch
ldaa #$FF ; $FF to RAM $E9, $DE, $DF, $E0, $E1, $B4, $C2, $E9, $E7
staa X00E9 ; Input code
staa X00DE
staa X00DF
staa X00E0
staa X00E1
staa X00B4
staa X00C2
staa X00E9 ; Input code (again...)
staa X00E7 ; Output code
ldd #$0080
std X00EE ; RAM $EE = $0080
cli
LF056:
ldaa X0002 ; Read port1
bita #$02 ; P11 is nSLOTCS ($02 is a mask, not a bit number)
beq LF08F ; Slot is enabled ->
clra
staa X0002 ; Clear port1
staa X00E2 ; Clear error counter ?
staa X00E5 ; Reset byte counter
staa X00E8
staa X00EA
staa X00EB ; Clear flags
staa X00F1 ; Clear status ?
staa X00F2
staa X00F3
deca
staa X00B4 ; $FF in RAM...
staa X00C2
staa X00DE
staa X00DF
staa X00E0
staa X00E1
staa X00E9 ; Input code
bra LF056 ; Loop until slot is enabled
; Slot enabled
LF08F:
inc X00F0 ; $F0 starts at 0, now 1
ldaa X00EB ; Got a byte from CPU ?
bita #$01
bne LF09C ; Yup ->
jmp LF193 ; Nope ->
; Process CPU write
LF09C:
; AIM AND Immediate $FE with RAM $EB (clear CPU write flag)
; EIM XOR Immediate $80 with RAM $F1 (toggle status bit 3)
ldaa X00F2
bne LF0B7
ldab X00E9 ; Input code
andb #$F0 ; Upper nibble is index in jump table
ldx #$F4DA
lsrb ; 0BBBB000
lsrb ; 00BBBB00
lsrb ; 000BBBB0
abx ; B+X -> X
ldx $00,x
jmp $00,x ; Index jump
;
LF0B7:
bita #$01
beq LF0DE
ldab X00E8
cmpb X00F3
beq LF117
ldx #$00D0
abx ; B+X -> X
ldaa X00E9 ; Input code
staa $00,x
ldaa $01,x
staa X0007 ; Port4 data (output code)
; AIM AND Immediate $EF with RAM $F1
ldaa X00F1 ; Status ?
staa X0002 ; Port1 data
inc X00E8
jmp LF193
;
LF0DE:
ldab X00E8
cmpb X00F3
beq LF0FC
ldx #$00D0
abx ; B+X -> X
ldaa $01,x
staa X0007 ; Port4 data (output code)
; AIM AND Immediate $EF with RAM $F1
ldaa X00F1 ; Status ?
staa X0002 ; Port1 data
inc X00E8
jmp LF193
;
LF0FC:
ldx #$00D0
abx ; B+X -> X
ldaa $00,x
coma
staa X0007 ; Port4 data (output code)
; AIM AND Immediate $EF with RAM $F1
ldaa X00F1 ; Status ?
staa X0002 ; Port1 data
clra
staa X00E8
staa X00F2
jmp LF193
;
LF117:
clra
staa X00F2
ldx #$00CF
abx ; B+X -> X
ldaa $00,x
coma
cmpa X00E9 ; Input code
beq LF13D
ldaa $01,x
coma
staa X0007 ; Port4 data (output code)
; OIM OR Immediate $20 with RAM $F1 (set status bit 1)
; AIM AND Immediate $EF with RAM $F1
ldaa X00F1 ; Status ?
staa X0002 ; Port1 data
clr X00E8
jmp LF193
;
LF13D:
ldab X00E7 ; Output code
cmpb #$FF
bne LF159
ldaa $01,x
staa X0007 ; Port4 data (output code)
; OIM OR Immediate $20 with RAM $F1 (set status bit 1)
; AIM AND Immediate $EF with RAM $F1
ldaa X00F1 ; Status ?
staa X0002 ; Port1 data
clr X00E8
jmp LF193
;
LF159:
ldaa $01,x
coma
staa X0007 ; Port4 data (output code)
clra
xgdx ?????
clr $DE,x
;
; AIM AND Immediate $CF with RAM $F1
ldaa X00F1 ; Status ?
staa X0002 ; Port1 data
clr X00E8
ldx X00EE
ldd X00D0
std $00,x
ldd X00D2
std $02,x
ldd X00D4
std $04,x
ldd X00D6
std $06,x
ldd X00D8
std $08,x
ldd X00DA
std $0A,x
ldaa X00DC
staa $0C,x
LF193:
ldaa X00EB ; Got a byte from link ?
bita #$02
bne LF19D ; Yup ->
jmp LF257 ; Nope ->
; Process link receive
LF19D:
; AIM AND Immediate $FD (11111101) with RAM $EB
ldab X00EC
bitb #$40 ; Overrun framing error ?
bne LF1AE ; Yup ->
bitb #$80 ; Receive data register full ?
bne LF1CE ; Yup ->
jmp LF257
; Overrun framing error
LF1AE:
clra
staa X00E5 ; Reset byte counter
staa X00EA
deca
staa X00C2
staa X00B4
inc X00E2 ; Error counter ?
ldaa X00F1 ; Status ?
oraa #$40 ; Set status bit 2
anda #$FE ; Mask out P10, just in case (transmit enable, not status)
staa X00F1 ; Status ?
staa X0002 ; Port1 data
jmp LF257
; Got byte ok
LF1CE:
ldab X00E5 ; Byte counter
cmpb #$0D
beq LF1E5 ; Already got 13 bytes ? ->
clra
xgdx ?????
ldaa X00ED ; Received code
staa $C2,x ; Store in list @ $C2+x
inc X00E5 ; Byte counter
; OIM OR Immediate $04 with RAM $EB
jmp LF257
; Got message OK
LF1E5:
; AIM AND Immediate $FE with RAM $F1
ldaa X00F1 ; Status ?
staa X0002 ; Port1 data
clra
xgdx ?????
ldaa X00ED ; Received code
staa $C2,x ; Store 14th byte (the last)
clra
staa X00EA
staa X00E5 ; Reset byte counter
deca
staa X00B4
ldaa X00C2 ; RAM $C2 (first byte of message) & 3: 0~3 -> 1~4, gives B=$02,$04,$08,$10
anda #$03
inca
ldab #$01
LF207:
aslb
deca
bne LF207
lsrb ; B=$01,$02,$04,$08
orab X00E4
stab X00E4
ldab X00C2
andb #$03
ldx #$00F4
abx ; X = $00F4 + (RAM $C2 & 3)
clr $00,x
cmpb X00E7 ; Output code
beq LF252
ldx #$F4FA
abx ; B+X -> X
abx ; B+X -> X
incb
andb #$03
stab X00E3
ldx $00,x
ldd X00C3
std $00,x
ldd X00C5
std $02,x
ldd X00C7
std $04,x
ldd X00C9
std $06,x
ldd X00CB
std $08,x
ldd X00CD
std $0A,x
ldaa X00CF
staa $0C,x
LF252:
ldaa #$FF
staa X00C2
LF257:
ldaa X00F0
cmpa #$28
bcs LF296
ldx #$00F4
ldab X00E3
abx ; B+X -> X
ldaa $00,x
inca
cmpa #$0A
bne LF27C
ldaa #$01
incb
LF26F:
asla
decb
bne LF26F
lsra
coma
anda X00E4
staa X00E4
clra
LF27C:
staa $00,x
inc X00E3
; AIM AND Immediate $03 with RAM $E3
clra
staa X00E5 ; Reset byte counter
staa X00EA
staa X00F0
; AIM AND Immediate $FE with RAM $F1
ldaa X00F1 ; Status ?
staa X0002 ; Port1 data
LF296:
ldaa X0011 ; Read TRCS
bita #$20 ; Transmit register empty ?
beq LF309 ; Nope ->
ldaa X00B4
cmpa #$FF
bne LF309
clra
ldab X00E7 ; Output code
cmpb #$FF
beq LF309
xgdx ?????
ldab $DE,x
bne LF309
orab X00EA
orab X00E5 ; Byte counter
bne LF309
xgdx ?????
eorb X00E3
bne LF309
ldx X00EE ; X=$00EE
ldd $00,x
std X00B5 ; RAM $B5 <- RAM $EE
ldd $02,x
std X00B7 ; RAM $B7 <- RAM $F0
ldd $04,x
std X00B9 ; RAM $B9 <- RAM $F2
ldd $06,x
std X00BB ; RAM $BB <- RAM $F4
ldd $08,x
std X00BD ; RAM $BD <- RAM $F6
ldd $0A,x
std X00BF ; RAM $BF <- RAM $F8
ldaa $0C,x
staa X00C1 ; RAM $C1 <- RAM $FA
ldaa X00E7 ; Output code
staa X00B4
; OIM OR Immediate $01 with RAM $F1 (P10 high, enable TX buffer in 75176)
ldab X00F1 ; Status ?
stab X0002 ; Port1 data
staa X0013 ; Transmit register
;
; AIM AND Immediate $FB with RAM $EB
inc X00EA
inc X00E3
; AIM AND Immediate $03 with RAM $E3
clra
ldab X00E7 ; Output code
xgdx ?????
ldaa #$FF
staa $DE,x
LF309:
ldaa X00EB
bita #$04
beq LF33F
ldaa X00F0
cmpa #$0F
bcs LF33F
ldaa X00B4
cmpa #$FF
beq LF33F
ldaa X0011 ; Read TRCS
bita #$20 ; Transmit register empty ?
beq LF33F ; Nope ->
ldab X00EA
cmpb #$0E
beq LF33F
;
; AIM AND Immediate $FB with RAM $EB
clra
xgdx ?????
ldaa $B4,x
inc X00EA
; OIM OR Immediate $01 with RAM $F1 (P10 high, enable TX buffer in 75176)
ldab X00F1 ; Status ?
stab X0002 ; Port1 data
staa X0013 ; Transmit register
LF33F:
jmp LF056
Command9:
sei
ldx #$0080
LF346:
clr $7F,x
dex
bne LF346
jmp LF000
Command0:
; AIM AND Immediate $EF with RAM $F1
ldaa X00F1 ; Status ?
staa X0002 ; Port1 data
jmp LF193
Command2:
ldaa X00E7 ; Output code
staa X0007 ; Port4 data (output code)
; AIM AND Immediate $EF with RAM $F1
ldaa X00F1 ; Status ?
staa X0002 ; Port1 data
jmp LF193
Command1:
ldaa X00E9 ; Input code
tab
anda #$0C ; Bits 2 and 3
bne LF3D6
; AIM AND Immediate $EF with RAM $F1
ldaa X00F1 ; Status ?
staa X0002 ; Port1 data
andb #$03
stab X00E7 ; Output code
ldx #$F4FA
abx ; B+X -> X
abx ; B+X -> X
ldd $00,x
std X00EE ; RAM $EE = $F4FA + X*2
ldab #$01
ldaa X00E9 ; Input code
anda #$03
LF38F:
deca
bmi LF396
aslb
jmp LF38F
;
LF396:
orab X00E4
stab X00E4
jmp LF193
Command4:
ldaa X00E9 ; Input code
anda #$0F
staa X00F3 ; RAM $F3 is lower nibble of input code
; AIM AND Immediate $EF with RAM $F1
ldaa X00F1 ; Status ?
staa X0002 ; Port1 data
ldaa #$FE
staa X00F2 ; RAM $F2 = $FE
jmp LF193
Command3/CommandA:
ldaa X00E7 ; Output code
cmpa #$FF
beq LF3D6 ; Is $FF ? ->
ldaa X00E9 ; Input code
anda #$0F
staa X00F3 ; RAM $F3 is lower nibble of input code
; AIM AND Immediate $EF with RAM $F1
ldaa X00F1 ; Status ?
staa X0002 ; Port1 data
ldaa #$FF
staa X00F2 ; RAM $F2 = $FF
jmp LF193
CommandD/E/F:
; OIM OR Immediate $10 with RAM $F1 (set status bit 0)
ldaa X00F1 ; Status ?
staa X0002 ; Port1 data
jmp LF193
Command5: ; Similar to command 1
ldaa X00E9 ; Input code
tab
anda #$0C ; Bits 2 and 3
bne LF3D6
; AIM AND Immediate $EF with RAM $F1
ldaa X00F1 ; Status ?
staa X0002 ; Port1 data
andb #$03
stab X00E6
ldx #$F4FA
abx ; B+X -> X
abx ; B+X -> X
ldx $00,x
ldd $00,x
std X00D1 ; RAM $D1 = $F4FA + X*2 (word)
ldd $02,x
std X00D3 ; RAM $D3 = $F4FA + X*2 + 2 (word)
ldd $04,x
std X00D5 ; RAM $D5 = $F4FA + X*2 + 4 (word)
ldd $06,x
std X00D7 ; RAM $D7 = $F4FA + X*2 + 6 (word)
ldd $08,x
std X00D9 ; RAM $D9 = $F4FA + X*2 + 8 (word)
ldd $0A,x
std X00DB ; RAM $DB = $F4FA + X*2 + A (word)
ldaa $0C,x
staa X00DD ; RAM $DD = $F4FA + X*2 + C (byte) always $FF ?
clr X00E8
jmp LF193
CommandC:
ldaa X00E7 ; Output code
cmpa #$FF
beq LF3D6
ldaa X00E9 ; Input code
tab
anda #$0C
bne LF3D6
; AIM AND Immediate $EF with RAM $F1
ldaa X00F1 ; Status ?
staa X0002 ; Port1 data
andb #$03
ldx #$F4FA
abx ; B+X -> X
abx ; B+X -> X
ldx $00,x
ldd $00,x
std X00D1
ldd $02,x
std X00D3
ldd $04,x
std X00D5
ldd $06,x
std X00D7
ldd $08,x
std X00D9
ldd $0A,x
std X00DB
ldaa $0C,x
staa X00DD
clra
staa X00E8
deca
staa X00F2
ldaa #$0D
staa X00F3
jmp LF193
Command6:
; AIM AND Immediate $EF with RAM $F1
ldaa X00F1 ; Status ?
staa X0002 ; Port1 data
ldaa X00E9 ; Input code
staa X00E8
jmp LF193
Command7:
XF48A:
ldaa X00E4
staa X0007 ; Port4 data (output code)
; AIM AND Immediate $EF with RAM $F1
ldaa X00F1 ; Status ?
staa X0002 ; Port1 data
jmp LF193
Command8:
ldaa X00E2 ; Error counter ?
staa X0007 ; Port4 data (output code)
; AIM AND Immediate $EF with RAM $F1
ldaa X00F1 ; Status ?
staa X0002 ; Port1 data
jmp LF193
CommandB:
ldaa X00F1 ; Status ?
anda #$BF
; AIM AND Immediate $EF with RAM $F1
staa X00F1 ; Status ?
staa X0002 ; Port1 data
jmp LF193
SC1:
ldaa X0011 ; Read TRCS
staa X00EC ; Store
ldaa X0012 ; Receive register
staa X00ED ; Store received code
clr X00F0
; OIM OR Immediate $02 with RAM $EB (link receive flag)
rti
IRQ1:
ldaa X000F ; Clear port3 latch flag
ldaa X0006 ; Port3 data (input code)
staa X00E9 ; Input code
; OIM OR Immediate $01 with RAM $EB (CPU write flag)
rti
XF4D6:
inc X00E2 ; Error counter ?
rti
XF4DA:
; CPU command 0: $F34E Update status
; CPU command 1: $F369
; CPU command 2: $F359 Read output code
; CPU command 3: $F3B7
; CPU command 4: $F39F
; CPU command 5: $F3E1
; CPU command 6: $F479 Put $E9 in $E8 ?
; CPU command 7: $F48A
; CPU command 8: $F49A Read error counter
; CPU command 9: $F342 Reset
; CPU command A: $F3B7 Same as command 3
; CPU command B: $F4AA Ack something ?
; CPU command C: $F426
; CPU command D: $F3D6 Invalid
; CPU command E: $F3D6 Invalid
; CPU command F: $F3D6 Invalid
XF4FA:
;0080 008D 009A 00A7 00B4 00C2 FF...