Introduction; The Opq Synthesizer Chip - Yamaha YM3806 Programmer's Manual

OPQ Programmer's Guide V 1.1
1

Introduction

This document contains a programmer's guide and a minimal data sheet for Yamaha OPQ
FM synthesizer chips. The information applies to YM3806 and very propably to YM3533
also.
There is no official information available for these chips. Everything presented in this
document is based on three sources:
•
Reverse engineering of Yamaha PSR-70 keyboard, by the author
◦ https://retroandreverse.blogspot.com/search/label/PSR-70%20reverse
%20engineering
•
Yamaha PSR-70 Owner's Guide, by Yamaha Corporation 1985
◦ http://www.synthmanuals.com/manuals/yamaha/psr-70/owners_manual /
•
Yamaha PSR-70 Service Manual, by Yamaha Corporation 1985
◦ https://elektrotanya.com/yamaha_psr-70_sm.pdf/download.html
One of the main information sources is the PSR-70 original internal software, which I have
studied closely. I will be referring to it several times with the term "PSR-70 firmware".
As a comparison and reference, I have used the more widely known OPL2/OPL3,
especially the excellent document "Programmer's Guide to Yamaha YMF 262/OPL3 FM
Music Synthesizer" by Vladimir Arnost. Testing things using Dexed soft synth ("closely
modeled on the original DX-7 characteristics") gave some insight. Also DX-11 seems to be
very close to OPQ in many respects.
The OPQ is not that widely used, but it is found at least in PSR-60, PSR-70 and CLP-100
keyboards.
2

The OPQ synthesizer chip

The PSR-70 unit used for reverse engineering contains YM3806 chip, so all first-hand
information here is from this chip. The Service Manual uses also name YM3533
interchangeably, so it should be the same chip.
The chip is meant to be connected to normal processor bus. Data bus is 8-bit wide and
there are 8 address lines. Bus control signals are the normal RD, WR and CS. The chip
can also request an interrupt.
OPQ chip contains no D/A-converter. It outputs two serial digital streams to an external
DAC. In PSR-70, an YM3012 is used for this purpose. A datasheet for YM3012 is available
in internet.
There is no bus timing information available. In PSR-70, a Z80 CPU with 6 MHz clock is
used and the OPQ chip is mapped as a part of memory address space. There is a wait-
3