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TRH9000

Yamaha V9990 based open-source video card for the MSX

TRH9000

Introduction

If you ever spent just a few minutes on YouTube searching for MSX content, I bet you certainly found some footage covering the V9990. Well, not specifically the V9990 chip, but video cards based on it.

The first video card based on the unreleased, kind of obscure Yamaha V9990 VDP chip was the Graphics9000 (or GFX9000). The GFX9000 is (was) a graphics expansion device for MSX computers developed by Sunrise in 1994.

It was designed as an expansion cartridge for the MSX standard that can be installed in a slot on a computer that also connects to the computer’s video output and monitor. The device works as an additional independent video controller.

The device is based on the Yamaha V9990 video controller (VDP). The chip was designed specifically for use in computers of the alleged but not implemented (by the time of this writing) MSX3 standard. The V9990 is not backward compatible with the V99x8 chips, and thus cannot be used as the main video controller of standard MSX-compatible computers.

The TRH9000

TRH9000 is an open-source implementation of the GFX9000, representing a community-driven effort to document everything necessary to build MSX cartridges that can run V9990 software.

TRH9000

TRH9000

The goal is to make those cards more accessible and improve the amount of software available for it.

Technical Information

The TRH9000 is a graphics expansion cartridge designed for MSX computers that was developed by a community of MSX enthusiasts as an open-source implementation of the GFX9000.

Selection Logic

For the TRH9000, the control logic is implemented by two ICs. According to the not exhaustive list of IO ports documented here. The IO ports used the by an GFX9000 compatible cartridge must be 60h~6Fh*. The 74HCT138 IC on the board performs the selection of those IO ports and with the aid of the 74HC32 performs the activation of the appropriate signals on the V9990 chip.

RAM chips

The KM428C256 RAM chip is the primary memory module used in the TRH9000. It is a CMOS 256K x 8 bit dual-port dynamic random-access memory (DRAM) chip that serves as the primary memory module in the cartridge. We use two memory chips, wired to the Yamaha V9990 VDP.

Connectors

On its latest version, the TRH9000 features three types of video output connectors: a DB15 RGB/VGA connector, a RCA composite connector and a mini-DIN 4 SVideo connector. The DB15 connector is a standard video connector that supports VGA, and RGB, making it a versatile choice for connecting to various types of displays. The SVIDEO signal, on the other hand, is a video signal that carries the chrominance and luminance components of the video separately, resulting in a higher quality image than composite video that is output on the RCA connector.

Video Output

RGB

The TRH9000 cartridge produces RGB signal with a horizontal frequency of 15.7KHz, which was the standard at the time of the V9990 chip's release. If you plan to connect the cartridge directly to your monitor using a VGA cable, it's important to ensure that your monitor supports synchronization at 15.7KHz.

You can see a list of modern monitors with support to 15.7KHz available at http://15khz.wikidot.com/

If you're not getting any image from the cartridge connector, it indicates that your monitor cannot sync at 15.7KHz. Typically, modern monitors can only sync at frequencies above 31KHz.

In such a scenario, you will require an adapter to upscale the frequency, making it compatible with your monitor. These adapters are commonly used for vintage video games and are readily available in various marketplaces. Here are a few options to consider:

Description Link
Alt text TZT HamGeek GBSC Converter GBS Control Retro Video Game Signal Converter Gaming Accessory Ali Express
Alt text OSSC HDMI-Compatible Converter Open Source Scan Adapter Kit with Game Cable for Retro Game Consoles Ali Express
Alt text Retrotink 2X Scart https://www.retrotink.com/product-page/retrotink-2x-scart

If you decide to use the Retrotink you will need a VGA to SCART cable. That is easy to solder and you need to connect the signals in the following way:

VGA SCART Signal
1 --> 15 Red
2 --> 11 Green
3 --> 7 Blue
5 --> 21 GND
13 --> 20 Sync

By request of the community, a jumper was included on the latest PCB version to provide optionally 5V on the pin 9 of the VGA connector. This is useful for those who want to use build a SCART cable that depending on the monitor may require 5V in some pins.

The jumper is located on the back of the PCB and is labeled as "JP1". The default position is open, so if you need to use it, you will need to close it with a solder blob.

Here is a diagram of the DH15 connector:

RGB pinout

S-Video and Composite

The TRH9000 cartridge provides support for both S-Video and Composite video outputs. These video signals are transmitted through respective connectors that are also located on the upper edge of the cartridge PCB.

Please note that only the S-Video signal is accessible on the pin header in v1.3. The Composite signal becomes available starting from the v1.4 version. Svideo and RCA Composite connectores are only available from v1.5 onwards.

To utilize these signals on v1.4 or v1.3, you'll need to construct a cable that links the pin header to the S-Video or Composite input of your monitor.

The pinout of the pin header is as follows:

SVideo and Composite pinout

As a reference the following image presents the pinout for S-Video and Composite connectors:

Alt text

Please use the tables shown below to build your cables.

  • S-SVIDEO uses COUT, YOUT and GND
Pin Svideo TRH9000 Pin Header Signal
1 - GND 2 - GND Ground
2 - GND 2 - GND Ground
3 - Y 3 - YOUT Luminance
4 - C 1 - COUT Chrominance
  • Composite uses CVOUT and GND
Pin Composite TRH9000 Pin Header Signal
SIGNAL 1 - CVOUT Composite Signal
GROUND 2 - GND Ground

For optimal cable construction and secure locking during use, I recommend using an XHB2.54 angled connector with a buckle. This item is available for purchase on Ali Express here.

Alt text

Below you can find some pictures of the TRH9000 cartridge connector and the SVIDEO cable. These images can help you better understand how to connect your cartridge to your monitor and ensure that you have a stable video output.

XHB2.54 Connector Soldered XHB2.54 Case Hole S-Video Cable Connected to TRH9000
SVIDEO1 SVIDEO2 SVIDEO3

Bill of Materials (v1.7)

TRH9000 Interactive BOM

References Value Footprint Qtd Link
C1, C6, C7, C8, C17, C19, C20, C22, C24 0.1uF C_0805_2012Metric 9 Ali Express
C9, C11, C12, C13, C14, C15, C26 220uF CP_EIA-3528-15_AVX-H 7 Ali Express
C3, C4 27pF C_0805_2012Metric 2 Ali Express
C5, C10 47pF C_0805_2012Metric 2 Ali Express
C16, C18 1uF C_0805_2012Metric 2 Ali Express
C23, C25 10nF C_0805_2012Metric 2 Ali Express
C2 10uF C_0805_2012Metric 1 Ali Express
C21 47uF CP_EIA-3528-15_AVX-H 1 Ali Express
R1, R3, R4, R5, R6, R10 4K7 R_0805_2012Metric 6 Ali Express
R14, R15, R16, R17, R18, R19 75R R_0805_2012Metric 6 Ali Express
R20,R21,R22 470R R_0805_2012Metric 3 Ali Express
R7, R12 2K2 R_0805_2012Metric 2 Ali Express
R2 10M R_0805_2012Metric 1 Ali Express
R8 1K R_0805_2012Metric 1 Ali Express
R9 100R R_0805_2012Metric 1 Ali Express
R11 220R R_0805_2012Metric 1 Ali Express
R13 3K3 R_0805_2012Metric 1 Ali Express
L1, L2 4.7uH L_0805_2012Metric 2 Ali Express
U4, U5 KM428C256 SOJ-40_400mil 2 UT Source
U1 74HC138 SO-16_3.9x9.9mm_P1.27mm 1 Ali Express
U2 74HC32 SO-14_3.9x8.65mm_P1.27mm 1 Ali Express
U3 V9990 LQFP-128_28x28mm_P0.8mm 1 The Retro Hacker Store
U6 CXA2075M SOP-24_7.5x15.4mm_P1.27mm 1 Ali Express
Y1 21.47727Mhz Crystal_HC49-U_Vertical 1 Ali Express
X1 14.31818MHz Oscillator_DIP-4 1 Ali Express
RV1, RV2, RV3 500R Potentiometer_Bourns_3314G_Vertical 3 Ali Express
Q1 BC817 SOT-23 1 Ali Express
J4 S-Video Mini DIN 4 Pin Connector 1 Ali Express
J2 RGB DSUB-15-HD_Female_Horizontal 1 Ali Express
J3 Composite RCA-2_Horizontal 1 Ali Express

Kudos

There are a few folks activelly helping with the project and I would like to call them out here:

  • Alexandre Souza
  • Doomn00b
  • Darlei Duarte
  • lintweaker
  • Luciano Sturaro
  • MetalGear2
  • sdsnatcher73
  • sdsnatcher
  • Thiago Valença
  • Wagner Tavares

License

Open Hardware

This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

  • If you remix, transform, or build upon the material, you must distribute your contributions under the same license as the original.
  • You may not use the material for commercial purposes.
  • You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.

ATTENTION

This project was made for the retro community and not for commercial purposes. So only retro hardware forums and individual people can build this project.

THE SALE OF ANY PART OF THIS PROJECT WITHOUT EXPRESS AUTHORIZATION IS PROHIBITED!

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Open Source MSX Graphics Card based on the Yamaha V9990 chip

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