Last update: August 1st 2012

Ti99Hdx hardware

This is a combined software and hardware project.

The Ti99Hdx project is an interface method to communicate with a PC via a serial (TI RS232/2 or own build) or parallel (Cf7a+) interface. For the TI side the interface acts like an ordinary mass storage device. In this way it is possible to load, save, open, read, write and close files. All the file data are send to the PC. On the PC runs a windows program which executes all the file commands.

This first version of the interface, which started around 1996 had an 8251 uart and a maximum baudrate of 19k2 baud. The second version (1998) was equiped with an 8255 parallel interface and also needed some special PC card. This version was much faster than the previous one. The next version (winter 2003) is again a serial model with a 16C550 uart and used a baudrate of 115K2 baud. This is mainly because you can't buy a PC anymore with an ISA bus for the parallel IO interface I used. The last version (summer 2008) uses the Texas Instruments RS232 card (PHP1220) with a baudrate 38K4 baud. In this case the original RS232 DSR prom is replaced by an 8Kb RAM to load the TI99HDX DSR which also contains the standard RS232 DSR.

Now there are three posibilities for using the Ti99Hdx project:

Using a Cf7a+ interface
This option uses the parallel port of the Cf7a+ interface. One extra connection must be made between the controller chip on the parallel port connector. A stripped down version of Dm2k called Cf7Pio can be used for transferring files. Other Ti99Hdx functionality are not available.
Using a nanoPEB interface
This option uses the serial port of the nanoPEB interface. A stripped down version of Dm2k called CfHdxS1 can be used for transferring files. Other Ti99Hdx functionality are not available. The baudrate for communicating with the PC is fixed at 38k4 baud, 8 databits, Even parity and one Stopbit.
Using a standard TI RS232 interface
This option uses the serial port RS232/1 of the original TI RS232 card. A stripped down version of Dm2k called CfHdxS1 can be used for transferring files. Other Ti99Hdx functionality are not available. The baudrate for communicating with the PC is fixed at 38k4 baud, 8 databits, Even parity and one Stopbit.
Using a modified TI RS232 interface
This option uses the serial port RS232/2 of the original TI RS232 card. A new DSR (in RAM) must be placed on the RS232 card. Al Ti99Hdx functionality is available. The baudrate for communicating with the PC is fixed at 38k4 baud, 8 databits, Even parity and one Stopbit.
Build your own RS232 interface
This is the most difficult option. A PEB card must be created with a 16C550 UART which wil give you the maximum communication speed of 115K2 baud.

Ti99Hdx Protocol

There is a description of the protocol and the read and write sequence to Intel chips with a TI99.