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Timers
To do: Page.
| Address (Z80 port 4)
|
Data (Z80 port 5)
|
| $24
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
TA counter load bits 9-2 |
|
| $25
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
- |
TA counter load bits 1-0 |
|
| $26
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
TB counter load bits 0-7 |
|
| $27
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
CSM mode |
3-slot mode | Reset TB | Reset TA | Enable TB IRQ | Enable TA IRQ | Load TB | Load TA |
|
- TA = Timer A (10bit), TB = Timer B (8bit)
- Timers will tick until they have reached zero, at which point an IRQ will be generated if enabled. Reading port $04 will show which timer caused it (see below).
- The actual timer counter registers are not directly accessible. They can be reset to zero or initialised from load registers $24~$26
- Writing 0 to the load bits in register $27 will reset the timer counter registers to zero
- Writing 1 to the load bits will copy the respective timer load register to the timer counter. This only works when the timer is at zero.
- When a timer expires, it is automatically reloaded from the load registers and continues.
- Timer flag reset refers to the same flags that are read from port $04
- CSM mode is for automatic key on for operators on the second FM channel when timer A expires ?
- Timer A IRQ frequency: 8M / 2 / 12 (prescaler) / 12 / TA load = 27.1Hz ~ 27.8kHz ?
- Timer A IRQ frequency: 8M / 16 / 12 (prescaler) / 12 / TB load = 13.6Hz ~ 3.47kHz ?
SSG part
See SSG for details on this part's operation.
| Address (Z80 port 4)
|
Data (Z80 port 5)
|
|
| $00
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
Fine tune |
|
Channel A
|
| $01
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
- |
Coarse tune |
|
| $02
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
Fine tune |
|
Channel B
|
| $03
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
- |
Coarse tune |
|
| $04
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
Fine tune |
|
Channel C
|
| $05
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
- |
Coarse tune |
|
| $06
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
- |
Noise tune |
|
Noise channel
|
| $07
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
- |
/EN noise C | /EN noise B | /EN noise A | /EN C | /EN B | /EN A |
|
/Enable for Noise and Tone
|
| $08
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
- |
Mode | Volume |
|
Channel A
|
| $09
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
- |
Mode | Volume |
|
Channel B
|
| $0A
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
- |
Mode | Volume |
|
Channel C
|
| $0B
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
Volume envelope period fine tune |
|
|
| $0C
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
Volume envelope period coarse tune |
|
|
| $0D
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
- |
Volume envelop shape |
|
See diagram.
|
FM part
See FM for details on this part's operation.
Common FM registers
| Address (Z80 port 4)
|
Data (Z80 port 5)
|
|
| $22
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
- |
On | Control |
|
LFO Frequency
|
| $28
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
Slot |
- | Channel |
|
Key On/Off
|
LFO frequency values are as follows:
- 0 – 3.98Hz
- 1 – 5.56Hz
- 2 – 6.02Hz
- 3 – 6.37Hz
- 4 – 6.88Hz
- 5 – 9.63Hz
- 6 – 48.1Hz
- 7 – 72.2Hz
Overall channel registers
The first value listed in the Address column is for channels 1/3; the second is for channels 2/4.
| Address (Z80 port 4 or 6) |
Data (Z80 port 5 or 7) |
|
| $A1,$A2
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
F-Num 1 |
|
F-Numbers and Block (1/2)
|
| $A5,$A6
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
- |
Block | F-Num 2 |
|
F-Numbers and Block (2/2)
(must set this first)
|
| $A9,$AA
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
2CH * F-Num 1 |
|
2CH - 2 Slot F-Numbers/Block (1/2)
|
| $AD,$AE
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
- |
2CH * Block | 2CH * F-Num 2 |
|
2CH - 2 Slot F-Numbers/Block (1/2)
(must set this first)
|
| $B1,$B2
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
- |
FB | ALGO |
|
Feedback (FB) and Algorithm (ALGO)
|
| $B5,B6
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
L |
R | AMS | - | PMS |
|
Left (L)/Right (R) output, AM Sense (AMS), and PM Sense (PMS)
|
Channel registers
Depending on which channel you want to write to, the ports used are different:
- Channels 1 & 2: Ports 4/5
- Channels 3 & 4: Ports 6/7
Per-operator registers
The ranges given for the address represent all of the parameter values. Each channel's operators are laid out as follows:
| Operator |
1 |
2 |
3 |
4
|
| Channels 1, 3
|
$x1 |
$x5 |
$x9 |
$xD
|
| Channels 2, 4
|
$x2 |
$x6 |
$xA |
$xE
|
| Address (Z80 port 4 or 6) |
Data (Z80 port 5 or 7) |
|
| $31-$3E
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
- |
DT | MUL |
|
Detune (DT) and Multiple (MUL)
|
| $41-$4E
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
- |
Total Level |
|
Total Level (Volume)
|
| $51-$5E
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
KS |
- | AR |
|
Key Scale (KS) and Attack Rate (AR)
|
| $61-$6E
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
AM |
- | DR |
|
AM On (AM) and Decay Rate (DR)
|
| $71-$7E
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
- |
SR |
|
Sustain Rate (SR)
|
| $81-$8E
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
SL |
RR |
|
Sustain Level (SL) and Release Rate (RR)
|
| $91-$9E
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
- |
SSG-EG |
|
SSG-EG
|
ADPCM part
See ADPCM for details on this part's operation.
| Address (Z80 port 4)
|
Data (Z80 port 5)
|
Value on reset
|
| $1C
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
B |
- | A6 | A5 | A4 | A3 | A2 | A1 |
|
$00
|
- Write to flag control to reset/mask channel end flags
- Write 1 to reset and/or mask selected flag
- Write 0 to unmask selected flag
- Masking a flag will prevent it from being raised when a channel reaches its end address. This means you have to write 1 to clear the flag, then 0 to keep it active.
- Flags must be manually cleared, playing a new sample on the channel won't clear it.
ADPCM-A part
See ADPCM for details on this part's operation.
| Address (Z80 port 6)
|
Data (Z80 port 7)
|
Value on reset
|
|
| $00
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
Dump |
- | CH6 ON | CH5 ON | CH4 ON | CH3 ON | CH2 ON | CH1 ON |
|
$00
|
'Dump' is the key on/off bit. Write 0 to start playing specified channels and write 1 to stop playing.
|
| $01
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
- |
Master volume |
|
$00
|
Actually an attenuator, 0 is the loudest.
|
| $08~$0D (one for each channel)
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
L |
R | - | Channel volume |
|
$00
|
Actually an attenuator, 0 is the loudest. L/R routes the output to the left and/or right channels.
|
| $10~$15 (one for each channel)
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
Sample's start address/256 LSB |
|
$00
|
All ADPCM addresses must match a 256-byte boundary (bits 0~7 = 0)
|
| $18~$1D (one for each channel)
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
Sample's start address/256 MSB |
|
$00
|
| $20~$25 (one for each channel)
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
Sample's stop address/256 LSB |
|
$00
|
| $28~$2D (one for each channel)
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
Sample's stop address/256 MSB |
|
$00
|
ADPCM-B part
See ADPCM for details on this part's operation.
| Address (Z80 port 4)
|
Data (Z80 port 5)
|
Value on reset
|
|
| $10
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
Start |
- | Repeat | - | Reset |
|
$00
|
Repeat: loop when end address is reached. Reset: clears Start and Repeat.
|
| $11
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
L |
R | - |
|
$00
|
Left/Right channel output
|
| $12
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
Sample's start address/256 LSB |
|
?
|
All ADPCM addresses must match a 256-byte boundary (bits 0~7 = 0)
|
| $13
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
Sample's start address/256 MSB |
|
?
|
| $14
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
Sample's stop address/256 LSB |
|
?
|
| $15
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
Sample's stop address/256 MSB |
|
?
|
| $19
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
Delta-N (L) |
|
?
|
Playback rate is f = 8M / 12 / 12 / (65535 / Delta-N) = 55555 * (Delta-N / 65535) Hz
|
| $1A
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
Delta-N (H) |
|
?
|
| $1B
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
ADPCM-B channel volume |
|
?
|
Loudest is $FF
|
Reading
The only writable registers that can also be read are from the SSG. All other ports and addresses return different data.
| Z80 port #
|
Data
|
Notes
|
| $04
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
Busy |
- | Timer B flag | Timer A flag |
|
When a timer expires and IRQ is enabled for the timer, the respective bit is set
|
| $05
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
SSG register data |
|
Attempting to read non-SSG registers will fail
|
| $06
|
| Bit |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| Def |
ADPCM-B end |
- | CH6 end | CH5 end | CH4 end | CH3 end | CH2 end | CH1 end |
|
When a channel has reached the end address and stops, the respective bit is set, unless masked
|
| $07
|
not implemented
|
Always returns $00
|