The
TI-99/4A
Tech Pages

These pages are dedicated to the Texas Instruments TI-99/4A home computer. They contain mainly technical information on the various processors and memory chips found in the console, on peripheral cards and cartridges and on additional hardware. Although the emphasis is on hardware, I included numerous examples of assembly language programs to demonstrate how to access hardware or illustrate undocumented features.

These pages are not for beginners! To follow the discussion you'll need some knowledge of digital electronics and notions of assembly language programming. I tried to adopt a fairly didactic style, but this is by no means a tutorial. Nevertherless, you'll find an assembly language primer, an introduction to GPL language, an explanatory page for digital TTL chips and tutorials on how to solder and how to open your console and PE-box.

These pages are meant to load fast over a phone line: no fancy graphics, no pictures inserted in the text and (God preserves us) no frames! In addition, the whole site is available for download as .zip files.

This site is currently hosted by the University of Geneva, Switzerland. It used to be hosted by Stanford, then the University of Sheffeild, but this changed when I moved back to my hometown. So if you've bookmarked the old site, please replace it with http://www.nouspikel.com/ti99/titechpages.htm

Now folks, I hate to brag,but I must admit that it feels good to be recognized by one's peers. So let it be known that this site was granted the Edgar Mauk Award in the catagorie `TI Websites`, at the European TI-Treffen in Gent (Belgium), on October 7th 2000. Click here for details.

In 2003, it was granted the Jim Peterson Award in the category "Community Service".

RTP award
And in 2005, it was selected for the Rob Tempelmans Plat award, a joint initiative from the Chicago TI users group and the Dutch TI Gebruikersgroep to honor the best internet sites for the TI-99/4A community.

Below is the site map. Note that some pages may be listed under more than one header.

The TI-99/4A console

General architecture
Pinout of ports and chips

Processors
TMS9900 CPU
TMS9901 Programmable system interface
TIM9904 Four-phase clock generator and driver
TMS9918A (or TMS9928A or TMS9929A) Videoprocessor
TMS9919 Sound generator
TMS5220 Speech synthesizer

Memory
ROMs
GROMs
Scratch-pad RAM
VDP RAM

Miscellaneous
Keyboard
CRU (communication register unit)
Interrupts
Cassette tape interface
TTL chips featured in the schematics on this site