jotego/jt5205

Verilog ADPCM decoder compatible with OKI MSM5205

jt5205 hardware by Jose Tejada (@topapate)

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JT5205 is an ADPCM sound source written in Verilog, fully compatible with OKI MSM5205.

Using JT5205 in a git project

If you are using JT5205 in a git project, the best way to add it to your project is:

1. Optionally fork JT5205's repository to your own GitHub account
2. Add it as a submodule to your git project: git submodule add https://github.com/jotego/jt5205.git
3. Now you can refer to the RTL files in jt5205/hdl

The advantages of a using a git submodule are:

1. Your project contains a reference to a commit of the JT5205 repository
2. As long as you do not manually update the JT5205 submodule, it will keep pointing to the same commit
3. Each time you make a commit in your project, it will include a pointer to the JT5205 commit used. So you will always know the JT5205 that worked for you
4. If JT5205 is updated and you want to get the changes, simply update the submodule using git. The new JT5205 commit used will be annotated in your project's next commit. So the history of your project will reflect that change too.
5. JT5205 files will be intact and you will use the files without altering them.

Port Description

Name	Direction	Width	Purpose
rst	input		active-high asynchronous reset signal
clk	input		clock
cen	input		clock enable.
sel	input	2	selects the data rate
din	input	4	input data
sound	output	12	signed sound output

Usage

This is a pin-to-pin compatible module with OKI MSM5205. If you are just going to use it on a retro core you don't need to know the internals of it just hook it up and be sure that the effective clock rate, i.e. clk&cen signal, is the intended 384kHz (or whatever your system needs).

If you hear a periodic noise when there should be no output, check whether your target system was leaving the MSM5205 halted at reset when no output was needed. If The part is not reset it will keep processing the output and a constant 0 input will produce a repetitive noise.

The VCLK output is by default a 1-clock cycle strobe suitable as a clock enable signal. To get a 50% duty cycle on it, instantiate the cell with the parameter VCLK_CEN set to zero.

FPGA arcade cores using this module:

• Double Dragon, by the same author
• Tora e no michi, by the same author

Related Projects

Other sound chips from the same author

Chip	Repository
YM2203, YM2612, YM2610	JT12
YM2151	JT51
YM3526	JTOPL
YM2149	JT49
sn76489an	JT89
OKI 6295	JT6295
OKI MSM5205	JT5205

jt5205's Issues

Master/slave mode

From the MAME sources:
https://github.com/mamedev/mame/blob/master/src/devices/sound/msm5205.cpp#L31

It's actually used on the Irem M62 sound board, where two of these chips are connected. Of course now it's possible to use the same lines to S1 and S2, and the chips will probably be in sync.

Support 3-bit samples (pin 3)

This one is connected on the Irem M62 sound board. However not sure if 3-bit samples are actually used in any game.