@nataliapc/mcp-openmsx

# FM-PAC / MSX-MUSIC (Yamaha YM-2413) In this text, only the direct programming of the MSX-MUSIC will be discussed, not the FM-BASIC possibilities, because they finally use direct control. The MSX-MUSIC or the FM-PAC uses two I/O ports for control. Unfortunately, these registers are only used to write from the computer to the FM-PAC, so reading registers from the FM-PAC/MSX-MUSIC is not possible. ``` 07Ch - Address port. 07Dh - Data Port. ``` To control these ports correctly in machine language, it is useful to use the following program: ``` ;Reg. D contains register number for FM-PAC. ;Reg. E contains data for selected register. SET_FM: LD A,D OUT (07CH),A LD A,E OUT (07DH),A EX (SP),HL ;These 2 commands only serve as a short EX (SP),HL ;pause for the PAC to process the data RET ;before sending new data. ``` ## Registers The FM-PAC contains 43 programmable registers for setting frequency, volume, instruments, drums and possibly samples. The latter is rather difficult, since the FM-PAC has no built-in hardware to play this independently like the MUSIC MODULE, a routine must be written in ML code for this, which sends the sample data in the FM-PAC via the necessary registers. so that it puts this sample on the sound output. ``` #0Fh FM.TST 7 6 5 4 3 2 1 0 ┌───┬───┬───┬───┬───┬───┬───┬───┐ │ - │ - │ - │ - │SND│ - │ - │SMP│ └───┴───┴───┴───┴───┴───┴───┴───┘ SND - 1=Sound output of the chip is out. SAMP - 1=Sample mode on, a four bit sample can be written to register #10h, the 4 highest bit. ``` ``` #10h - #18h LOWFRQ 7 6 5 4 3 2 1 0 ┌───┬───┬───┬───┬───┬───┬───┬───┐ │FQ7│FQ6│FQ5│FQ4│FQ3│FQ2│FQ1│FQ0│ └───┴───┴───┴───┴───┴───┴───┴───┘ ``` ``` #20h - #28h SELECT 7 6 5 4 3 2 1 0 ┌───┬───┬───┬───┬───┬───┬───┬───┐ │ - │ - │SUS│KEY│OC2│OC1│OC0│FQ8│ └───┴───┴───┴───┴───┴───┴───┴───┘ FQ 8/0 - Frequency from channel 1 to 9. OC 2/0 - Octave from channel 1 to 9. KEY - If a new tone has to be struck it must first be set to 0. Then the new data can be loaded (Frequency, Instrument and volume), then set this bit back to 1. SUS - If this bit is set to 1, the tone will slowly fade after the KEY bit is set to 0. If SUS is at 0, the tone will stop immediately when the KEY bit is turned off. ``` ``` #30h - #38h VOLINS 7 6 5 4 3 2 1 0 ┌───┬───┬───┬───┬───┬───┬───┬───┐ │IN3│IN2│IN1│IN0│VL3│VL2│VL1│VL0│ └───┴───┴───┴───┴───┴───┴───┴───┘ VL 3/0 - Volume from channel 1 to 9. At binary 0000 the highest volume is reached. IN 3/0 - Instruments from channels 1 to 9. There are 16 instruments, instrument number 0 of which can be programmed via registers #00 to #07. NR: Instrument: 00 Software Instrument 01 Violin 02 Guitar 03 Piano 04 Flute 05 Clarinet 06 Oboe 07 Trumpet 08 Organ 09 Tube 10 Synthesizer 11 Harpsicord 12 Vibraphone 13 Synthesizer Bass 14 Electric Piano 1 15 Electric Piano 2 ``` ``` #03h DRMSEL 7 6 5 4 3 2 1 0 ┌───┬───┬───┬───┬───┬───┬───┬───┐ │ - │ - │SEL│BD │SD │TOM│CIM│HH │ └───┴───┴───┴───┴───┴───┴───┴───┘ SEL - If this is bit 1, channels 7 to 9 will be used for drum settings, and bits 4 to 0 can be used to control a drum. BD - Bass Drum :1 = Activate, if SEL is set to 1. SD - Snare Drum. TOM - Tom-Tom. CIM - Cimbal. HH - Hi Hat. ``` The Drum's frequencies and volumes are divided as follows: ``` Reg: Use: #16h Frequency bit 7 to 0 for the BassDrum. #17h Frequency bit 7 to 0 for the SnareDrum and the HiHat. #18h Frequency bit 7 to 0 for the TomTom and the Cimbal. #26h Octave bit 2 to 0 and Frequency bit 8 for BassDrum. #27h Octave bit 2 to 0 and Frequency bit 8 for SnareDrum & the HiHat. #28h Octave bit 2 to 0 and Frequency bit 8 for Tom-Tom & the Cimbal. #36h Low nibble is volume of Bass Drum (0 is the highest volume). #37h High nibble is volume from Hi Hat. Low nibble is volume from Snare Drum. #38h High nibble is volume from Cimbal. Low nibble is volume from Tom-Tom. ``` ## Programming the Software Instrument. The FM contains 2 operators for each instrument. The sound is generated via the FM synthesis, which stands for Frequency Modulation. The System works the same as that of the Music-module/MSX-Audio only the maximum values will not always match, but the theory is the same. ``` #00h/01h SET.B / SET.A. 7 6 5 4 3 2 1 0 ┌───┬───┬───┬───┬───┬───┬───┬───┐ │ AM│VBR│S/D│RKS│MS3│MS2│MS1│MS0│ └───┴───┴───┴───┴───┴───┴───┴───┘ #00h for operator B and # 01h for operator A. AM - Amplitude Modulation. VBR - Vibrato. S/D - 0 = Decay; 1 = Sustain. RKS - Rate Key Scale. MS3/0 - Multi sample wave selection. ``` ``` #02h KSCMOD 7 6 5 4 3 2 1 0 ┌───┬───┬───┬───┬───┬───┬───┬───┐ │LK1│LK0│MD5│MD4│MD3│MD2│MD1│MD0│ └───┴───┴───┴───┴───┴───┴───┴───┘ LK1/0 - Level Key Scale. MD5/0 - Modulation Control. ``` ``` #03h FEED 7 6 5 4 3 2 1 0 ┌───┬───┬───┬───┬───┬───┬───┬───┐ │LK1│LK0│ - │DS2│DS1│FD2│FD1│FD0│ └───┴───┴───┴───┴───┴───┴───┴───┘ LK1/0 - Level Key Scale. DS2/1 - Distorted Wave Form. FD2/0 - FM-Feedback constant. ``` ``` #04h / #05h CTRL.B / CTRL.A 7 6 5 4 3 2 1 0 ┌───┬───┬───┬───┬───┬───┬───┬───┐ │AT3│AT2│AT1│AT0│DC3│DC2│DC1│DC0│ └───┴───┴───┴───┴───┴───┴───┴───┘ AT3/0 - Attack envelope rate. DC3/0 - Decay envelope rate. ``` ``` #06h / #07h IND.B / IND.A 7 6 5 4 3 2 1 0 ┌───┬───┬───┬───┬───┬───┬───┬───┐ │IN3│IN2│IN1│IN0│RL3│RL2│RL1│RL0│ └───┴───┴───┴───┴───┴───┴───┴───┘ IN3/0 - Indication Decay / Sustain level. RL3/0 - Release envelope rate. ``` The FM synthesis is quite complicated, especially for the beginner it is just a matter of trying. Fortunately, there are quite a few music programs on the market that handle this themselves.