Table of Contents
ECB-VGM
The ECB-VGM is a sound card for Z80 ECB systems.
It is intended to be a small format card that replicates the sound capabilities of the Sega Genesis. The Genesis featured the Yamaha YM2612 and Texas Instruments SN76489 sound chips. This unlikely match lead to the development of the VGM sound format (Video Game Music). There are many reincarnations of the original Sega design using modern processors with the YM2612/SN76489 combo.
Features
- Low cost 10×10 board form factor
- YM2612 Sound chip
- 2xSN76489 Sound chips
- Integrated preamp and audio amp.
- Terminal connector for speaker.
- VGM Player software included in ROMWBW
- SN76489's supported in ROMWBW
The discrete nature of the amplifier is intentional, to maintain the retro feel.
Note
The YM2612 is becoming hard to find and fakes are common. The YM3438 is pin compatible and can be substituted.
Some fake YM2612's are actually relabelled YM3438's. A real YM2612 runs warm to the touch whereas YM3438's runs cold.
Status
SN76489s and YM2612 and YM3438 tested and working. VGM files play.
Version 001C is current version, which including corrections from version 001B and refinements but is untested.
Refer to the development page for more information.
Files
Gallery
 |  |  |  |  |
 |
Port map
Eight ports are decoded for I/O access to the device
| Device | Port | Description | Notes |
|---|---|---|---|
| YM2612 | #C0 | ||
| “ | #C1 | ||
| “ | #C2 | ||
| “ | #C3 | ||
| SN76489 | #C4 | ||
| “ | #C5 | ||
| “ | #C6 | Device #1 Left Channel | |
| “ | #C7 | Device #2 Right Channel |
Jumpers
SW1 sets the port address and the WAIT line used by the SN76489s. The default port address is C0 and WAIT enabled.
| ADDR | SETTING |
|---|---|
| A3 | ON |
| A4 | ON |
| A5 | ON |
| A6 | OFF |
| A7 | OFF |
| WAIT | ON |
If the WAIT line is not used then software delays must be used when accessing the SN76489's.
SW2 Selects the power source for the LM386s
| SETTING | MEANING |
|---|---|
| 1-2 | Default - Use +5V bus power |
| 2-3 | Use external power connector (+5V to +12V) |
SW3 Select the Reset compatibility for the ECB System
| SETTING | MEANING |
|---|---|
| 1-2 | Default - Kontron reset method |
| 2-3 | Legacy reset method |
Software
Software support for the SN76489's can be enabled in ROMWBW by adding the following to your customer configuration files:
sbc_cust.asm
SN76489ENABLE .SET TRUE ; SN76489 SOUND DRIVER
The YM2612/YM3438's are currently not supported by ROMWBW HBIOS.
The VGMPlayer software and associated sample tunes resides in the following ROMWBW directories respectively: RomWBW\Source\Apps\VGM\vgmplay.com RomWBW\Source\Apps\VGM\Tunes
The VGMPlayer software needs to be customized for your processor speed by adjusting the FRAME_DLY setting.
VGM Music
Note that the CP/M memory size limits which files can be loaded and played.
Acknowledgements
The major components of this design have been taken from other project and used as building blocks for this design.
Aidan Lawrence -Aidan Lawrence's Mega MIDI: A Playable Version of my Hardware Sega Genesis Synth
J.B. Langston - J.B. Langston's RC2014 SN76489 board
Marco Maccaferri - VGMPlayer (Also based on J.B. Langston's work)
I can be contacted on the retrobrew forum as b1ackmai1er.
