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The FM part has '''4 channels''', each having their own operators, panning and amplitude values.
The FM ('''F'''requency '''M'''odulation) is part of the {{Chipname|YM2610}} sound chip. It provides '''4 channels''', each having their own set of 4 operators, panning and amplitude values. It's the most used way of producing music in games.
It's the most used way of producing music in games.


See [[YM2610 registers#FM|YM2610 registers: FM]]
=Common registers=
 
{|class="wikitable"
!Address (Z80 port 4)
!Data (Z80 port 5)
|
|-
|$22
|{{8BitRegister|-|4|On|1|Control|3}}
| LFO control and frequency (see below).
|-
|$28
|{{8BitRegister|Slot|4|-|1|Channel|3|}}
| Key On/Off for each channel.
|}
 
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
 
Channel numbering: 1, 2, 4, 5 instead of 1, 2, 3, 4 ?
 
=Channel registers=
 
Depending on which channel you want to write to, the {{Chipname|Z80}} ports used are different:
* Channels 1 & 2: Ports 4/5
* Channels 3 & 4: Ports 6/7
 
{|class="wikitable"
!colspan=4|Address||colspan=4|Data||rowspan=3|
|-
|CH1||CH2||CH3||CH4||CH1||CH2||CH3||CH4
|-
|colspan=2|Port 4||colspan=2|Port 6||colspan=2|Port 5||colspan=2|Port 7
|-
|$A1||$A2||$A1||$A2
|colspan=4|{{8BitRegister|F-Num 1|8}}
|F-Numbers and Block (1/2)
|-
|$A5||$A6||$A5||$A6
|colspan=4|{{8BitRegister|-|2|Block|3|F-Num 2|3}}
|F-Numbers and Block (2/2)<br/>(must set this first)
|-
|$A9||$AA||$A9||$AA
|colspan=4|{{8BitRegister|2CH * F-Num 1|8}}
|2CH - 2 Slot F-Numbers/Block (1/2)
|-
|$AD||$AE||$AD||$AE
|colspan=4|{{8BitRegister|-|2|2CH * Block|3|2CH * F-Num 2|3}}
|2CH - 2 Slot F-Numbers/Block (1/2)<br/>(must set this first)
|-
|$B1||$B2||$B1||$B2
|colspan=4|{{8BitRegister|-|2|FB|3|ALGO|3}}
|Feedback (FB) and Algorithm (ALGO)
|-
|$B5||$B6||$B5||$B6
|colspan=4|{{8BitRegister|L|1|R|1|AMS|2|-|1|PMS|3}}
|Left (L)/Right (R) output, AM Sense (AMS), and PM Sense (PMS)
|}
 
=Operator registers=
The ranges given for the address represent all of the parameter values. Each channel's operators are laid out as follows:
 
{|class="wikitable"
! Operator || 1 || 2 || 3 || 4
|-
! Channels 1, 3
| $x1 || $x5 || $x9 || $xD
|-
! Channels 2, 4
| $x2 || $x6 || $xA || $xE
|}
 
{|class="wikitable"
!colspan=4|Address||colspan=4|Data||rowspan=3|
|-
|CH1||CH2||CH3||CH4||CH1||CH2||CH3||CH4
|-
|colspan=2|Port 4||colspan=2|Port 6||colspan=2|Port 5||colspan=2|Port 7
|-
|colspan=4|$31-$3E
|colspan=4|{{8BitRegister|-|1|DT|3|MUL|4}}
|Detune (DT) and Multiple (MUL)
|-
|colspan=4|$41-$4E
|colspan=4|{{8BitRegister|-|1|Total Level|7|}}
|Total Level (Volume)
|-
|colspan=4|$51-$5E
|colspan=4|{{8BitRegister|KS|2|-|1|AR|5}}
|Key Scale (KS) and Attack Rate (AR)
|-
|colspan=4|$61-$6E
|colspan=4|{{8BitRegister|AM|1|-|2|DR|5}}
|AM On (AM) and Decay Rate (DR)
|-
|colspan=4|$71-$7E
|colspan=4|{{8BitRegister|-|3|SR|5}}
|Sustain Rate (SR)
|-
|colspan=4|$81-$8E
|colspan=4|{{8BitRegister|SL|4|RR|4}}
|Sustain Level (SL) and Release Rate (RR)
|-
|colspan=4|$91-$9E
|colspan=4|{{8BitRegister|-|4|SSG-EG|4}}
|Envelope generator (not to be confused with the [[SSG]] one)
|}


[[Category:Audio system]]
[[Category:Audio system]]

Revision as of 09:59, 18 February 2017

The FM (Frequency Modulation) is part of the YM2610 sound chip. It provides 4 channels, each having their own set of 4 operators, panning and amplitude values. It's the most used way of producing music in games.

Common registers

Address (Z80 port 4) Data (Z80 port 5)
$22
Bit 7 6 5 4 3 2 1 0
Def - OnControl
LFO control and frequency (see below).
$28
Bit 7 6 5 4 3 2 1 0
Def Slot -Channel
Key On/Off for each channel.

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

Channel numbering: 1, 2, 4, 5 instead of 1, 2, 3, 4 ?

Channel registers

Depending on which channel you want to write to, the Z80 ports used are different:

  • Channels 1 & 2: Ports 4/5
  • Channels 3 & 4: Ports 6/7
Address Data
CH1 CH2 CH3 CH4 CH1 CH2 CH3 CH4
Port 4 Port 6 Port 5 Port 7
$A1 $A2 $A1 $A2
Bit 7 6 5 4 3 2 1 0
Def F-Num 1
F-Numbers and Block (1/2)
$A5 $A6 $A5 $A6
Bit 7 6 5 4 3 2 1 0
Def - BlockF-Num 2
F-Numbers and Block (2/2)
(must set this first)
$A9 $AA $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 $AD $AE
Bit 7 6 5 4 3 2 1 0
Def - 2CH * Block2CH * F-Num 2
2CH - 2 Slot F-Numbers/Block (1/2)
(must set this first)
$B1 $B2 $B1 $B2
Bit 7 6 5 4 3 2 1 0
Def - FBALGO
Feedback (FB) and Algorithm (ALGO)
$B5 $B6 $B5 $B6
Bit 7 6 5 4 3 2 1 0
Def L RAMS-PMS
Left (L)/Right (R) output, AM Sense (AMS), and PM Sense (PMS)

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 Data
CH1 CH2 CH3 CH4 CH1 CH2 CH3 CH4
Port 4 Port 6 Port 5 Port 7
$31-$3E
Bit 7 6 5 4 3 2 1 0
Def - DTMUL
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
Envelope generator (not to be confused with the SSG one)
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