Yamaha FM-Sound Synthesizer Unit documentation Ver:1.0 Made By:
	General
	This document contains short description about programming FM sound Synthesizer (YM2151) of the FM sound synthesizer unit(II), that was made by Yamaha for CX5M MSX computer, but that was also available for other MSX computers trough Yamaha Unit Connector UCN-01. This unit includes also D/A converter (YM3012), so 8 audio tone signals can be obtained at the R and L channels. The YM2151 has 8-note capability and it is also equipped with a noise generator, vibrato oscillator, amplitude modulation circuit, tonal effect generator and timer circuitry. 2 sets of timers are used and when a timer overflows an interrupt request takes place. This unit has also YM2148 chip, that has a MIDI function, keyboard scan function and it supports MODE 2 IRQ for CPU, but this document does not tell, how to use these features. Addresses, that are needed for accessing this chip can be anyway founded from address table.
	How to find the FM-Sound Synthesizer Unit
	Because Yamaha made a Unit Connector, that can be inserted to any expansion slot, it is not sure, that this Unit is always connected to slot #3. That means, that you have to find this with your own routine. The standard way to do that is to search text "MCHFM0" from address #80 in every slot. Here is a simple routine to do that, activate this slot, run your FM-program part and exit to previous routine.   LD HL,BBEGIN LD DE,BEGIN LD BC,END-BEGIN LDIR JP BEGIN   BBEGIN   ORG #4000   BEGIN   DI ; Interrupts must be disabled, other ways we can't ; switch slots in #0000-#3FFF area.   LD (TOHL),SP ; We have to be sure, that SP is in area #4000-#BFFF   LD HL,0   TOHL     EQU $-2     LD SP,#8000 PUSH HL IN A,(#A8) PUSH AF AND %00111100 LD D,A LD B,3   SEARCHM ; Loop to search from main-slots.   LD A,B RRCA RRCA OR B OR D OUT (#A8),A PUSH BC LD A,(#FFFF) CPL PUSH AF AND %11111100 LD E,A LD B,3   SEARCHS ; Inner loop for sub slot search.   LD A,B OR E LD (#FFFF),A EXX LD B,6 LD HL,IDTXT-1 LD DE,#80-1   SEID     INC HL INC DE LD A,(DE) CP (HL) JR NZ,NOMATCH DJNZ SEID   ; It was found, so we will call a main program (you have to make that one), ; and after that we will select a slot, that was selected before running ; this part and we will exit with C flag as zero.   CALL FM_PROGGRAM POP AF LD (#FFFF),A POP AF POP AF OUT (#A8),A POP HL LD SP,HL XOR A RET   IDTXT     DEFB "MCHFM0"   NOMATCH     EXX DJNZ SEARCHS POP AF LD (#FFFF),A POP BC DJNZ SEARCHM   ; We didn't find it, and we will set C flag to detect an error   POP AF OUT (#A8),A POP HL LD SP,HL SCF RET
	Address Table
	#3FF0 (R) FM Status register #3FF0 (W) FM Address register #3FF1 (R/W) FM Data register #3FF2 (R/W) Yamaha external keyboard (YK-01 or YK-10) I/O address. #3FF3 (W) MIDI IRQ vector address #3FF4 (W) External IRQ vector address #3FF5 (R/W) MIDI UART Data read and write buffer #3FF6 (R) MIDI UART Status Register #3FF6 (W) MIDI UART Command Register
	Using the FM-Chip (Ready for write, timer overflows)
	Status register 7 6 5 4 3 2 1 0 BUSY           Timer B Timer A Writeable registers Register #00 (Not used) Register #01 (Test & LFO reset) 7 6 5 4 3 2 1 0             LFO R   Register #02 - #07 (Not used) Register #08 (Key on) 7 6 5 4 3 2 1 0   MOD1 CAR1 MOD2 CAR2 Channel Number Register #09 - #0E (Not used) REGISTER : #0F (NOISE ENABLE, NOISE FREQUENCY) 7 6 5 4 3 2 1 0 NE     Noise Frequency Register #10 (Not used) Register #11 (Clock A1) 7 6 5 4 3 2 1 0 B9 B8 B7 B6 B5 B4 B3 B2 Register #12 (Clock A2) 7 6 5 4 3 2 1 0             B1 B0 Register #13 (Clock B) 7 6 5 4 3 2 1 0 B7 B6 B5 B4 B3 B2 B1 B0 Register #14 (Clock Functions) 7 6 5 4 3 2 1 0 CSM   F RESET IRQ EN LOAD Register #15 - #17 (Not used) Register #18 (Low Frequency) 7 6 5 4 3 2 1 0 LOW OSCILLATION FREQUENCY Register #19 (Phase and Amplitude modulation) 7 6 5 4 3 2 1 0 F PHS OR AMP MODULATION DEPTH (F=0: Amplitude, F=1: Phase) Register #1A (Not used) Register #1B (Control output & wave form select) 7 6 5 4 3 2 1 0 CT2 CT1         Wave Form WF= 0 WF=1 WF=2 WF=3 SAW SQUARE TRIANGLE NOISE Register #1C-1F (Not used) Register #20 (Channel control) 7 6 5 4 3 2 1 0 RGT LFT FB CONNECT Register #28-2F (Key code) 7 6 5 4 3 2 1 0   Octave Note Register = #28 + Channel number (0-7) Register #30-37 (Key Fraction) 7 6 5 4 3 2 1 0 Key Fraction     Register = #30 + Channel number (0-7) Register #38-3F (Phase & amplitude modulation sensitivity) 7 6 5 4 3 2 1 0   PMS     AMS Register = #38 + Channel number (0-7) Register #40-5F (Detune & phase multiply) 7 6 5 4 3 2 1 0   Detune(1) Phase multiply Register = #40 + 8 * DEV* + Channel number (0-7) Register #60-7F (Total level) 7 6 5 4 3 2 1 0   Total level Register = #60 + 8 * DEV* + Channel number (0-7) Register #80-9F (EG Attack) 7 6 5 4 3 2 1 0 KeyScl   Attack rate Register = #80 + 8 * DEV* + Channel number (0-7) Register #A0-BF (EG Decay 1) 7 6 5 4 3 2 1 0 ASE     First decay rate Register = #A0 + 8 * DEV* + Channel number (0-7) ASE = Amplitude modulation Sensitivity Enable (1=enable) Register #C0-DF (EG Decay 2) 7 6 5 4 3 2 1 0 Detune(2)     Second decay rate Register = #C0 + 8 * DEV* + Channel number (0-7) Register #E0-FF (EG Decay level, Release rate) 7 6 5 4 3 2 1 0 First decay level Release rate Register = #C0 + 8 * DEV* + Channel number (0-7) * If you change value of MODULATOR1 then DEV=0 If you change value of MODULATOR2 then DEV=1 If you change value of CARRIER1 then DEV=2 If you change value of CARRIER2 then DEV=3
	How to handle external Yamaha keyboard
	Yamaha keyboards are easy to use. They have been divided to 8 separate rows, that each have 6 keys. When you want to read some key, you first have to select a row to read. This is done by sending this row number to #3FF2 in format: 7 6 5 4 3 2 1 0 ROW7 ROW6 ROW5 ROW4 ROW3 ROW2 ROW1 ROW0 This means, that you can calculate current row by using formula: [to #3FF2] = 2 ^ [ROW NUMBER 0-7] After this you need to wait a little while. Unfortunately I don't know how little, but something like one microsecond. Then you can read this address, and you will get a value in following format: 7 6 5 4 3 2 1 0   KEY5 KEY4 KEY3   KEY2 KEY1 KEY0 1=Not pressed 0=Pressed Current key number from bottom to up can be calculated by using formula: KEYNUMBER + ROW * 6 Please note, that YK-01 does not have few bottom keys at all.
	Rest that I want to say
	I want to thank "Greg_" about helping me to collect this information, I mean, that this information is not a offical documentation, but I have just collected it from different sources and rest is just generated by testing. Here are the Yamaha part-numbers for the most important chips, that are in FM-Sound Synthesizer Unit: YM2151 (IC101): #IT-21-51-00 (FM-chip) YM3012 (IC102): #IT-30-12-00 (Stereo D/A converter) YM2148 (IC103): #IT-21-46-00 (Midi handling) YM22702 (IC104): #IT-22-70-20 (ROM) Greetings: