"FM Sound" is to be implemented in "ZXSpectrumNext". However, it seems that FM Sound core was not developed. And the core development was completed on September 16, 2018 release.
PiyoTaro wrote: ↑Sun Mar 24, 2019 4:11 pmAppend: 2019/4/13
1. I am requesting "sound expansion for the game BGM". I'm not an instrument store.
2. I thought that the specification of "ZXSpectrumNext 's extension port" could be connected to the original ZXSpectrum 3+ peripherals.
However, I found a conversation in FB that "the expansion mode can not be used in" turbo mode ".
I have written my thoughts at the beginning of this thread because there was a reply of an incorrect explanation (the logic IC "74HC" series can not drive TTL5V !?).
The sound feature of ZX Spectrum Next, "Turbo Sound Next" adds features to the upper bits of AY's registers. Therefore, if you replace it with an AY compatible chip such as YM2203, the expanded register will overlap.
In the first place,"Turbo Sound" is a mechanism that stores bit0 when 255/254 is written to the AY register port and switches two sound chips with bit0.
"Turbo Sound Next" switches 3 sound chips with lower 2 bits.
I posted a circuit diagram with "bit2 =0" as the expansion board select signal.
But my circuit is not compatible with "Turbo Sound FM". So I tried to find a simpler address decoder.
ZXSpectrum compatible "Timex TS2068/TC2068" has its own sound extension.
The 8-bit I/O bus 0xF5 is assigned to the AY register port, and 0xF6 is assigned to the AY data port.
In addition, bit8 and bit9 are assigned to the selection of 1 and 2 of joystick port by the address of 16-bit I/O bus.
- Wiki of "ZXSpectrumNext official site (this site)"
Board feature control http://devnext.referata.com/wiki/Board_feature_control
- Martin Korth's document "Sinclair ZX Specifications"
Spectrum Sound PSG http://problemkaputt.de/zxdocs.htm#spec ... dgenerator
Spectrum Joystick Ports http://problemkaputt.de/zxdocs.htm#spec ... stickports
I tried to draw an address decoder circuit with this specification.
By using the 16-bit I/O bus bits, there is no need to use flip-flops in the chip select circuit. In this circuit, only two logic ICs are required.
(*April,14th "Cannot access the Expansion bus (edge connector) in Turbo mode" Therefore, I changed the logic IC to "74HC" family product.) This project aims at a small FM sound card that can be put on the pin header terminal CN5 (on the ZX Spectrum Next board).
- Z80 I/O address:"xxxx xxxN 1111 01NN b"
0x00F5: OPN2 bank 0 address
0x00F6: OPN2 bank 0 data
0x01F5: OPN2 bank 1 address
0x01F6: OPN2 bank 1 data
Connect the output of the sound board to the ZX Spectrum Next "EAR terminal (sound output)" and connect it to the audio equipment with the "Resistor included" Audio cable.
(Postscript.2019/4/21) I found an application manual translated into English of "YM2612" compatible with YM3438.
The difference between OPN2 and "OPN YM2203" is "Register B4H + - stereo; LFO sensitivity" ?
"Sega Genesis Technical Manual-YM2612 section" (from the personal site "Maxim's World of Stuff"): http://www.smspower.org/maxim/Documents/YM2612#regb0
"TFM Music Maker", a Windows app, is a tool for "Turbo Sound FM", but it can also emulate a sound chip and play music.
This app is a tool for "Turbo Sound FM" and can edit instrument sound data for OPN and compose 6 channels. There is also a function to export music data for Sega MegaDrive.
Link (Russian) http://www.nedopc.com/soft.php
(English translation)https://translate.google.com/translate? ... 2Fsoft.php
I would like to make a prototype with the following circuit diagram. If the clock generator is 8MHz as per the data sheet, the "PSG clock" will be 2MHz. (The tone parameters are compatible with Japanese PC-8801, FM-TOWNS, etc.)
(Postscript.2019/4/21: I also got an additional 3.579 × 2 = "7.158 MHz" clock gen.)
If possible, I would like to use the same frequency as the mega drive, 7.670442MHz, or 7MHz equivalent to ZX/48K which will be used in "Turbo Sound FM". (I also learned how to buy a custom-made oscillator. It seems that 10 unit prices will be about the same price as 1 unit sale.) However, it is not a project that sells as a parts kit, but it is assumed that each can collect and work on existing parts.
(*April 14th, I revised the circuit diagram.)
I would like to prototype with this circuit diagram. The amplification gain of the op-amp TL072 is based on the "Mega Amp" project. (Ri=51k, Rf=160k=82k+82k, Cf=47pF) (2019/4/18 Corrected Ri=not 39k. I realized that "GOAC YM3438" is not a discrete YM3438 FM chip. Also, I intend to make prototypes by replacing "Rf" with 82k+82k, and want to compare the loudness of the sound with "Turbo Sound Next". And there are small mistakes in this Rev2 schematic.)
Also, the clock generator is not wired in the schematic.