Texas Instruments CA-800 Cassette Interface

Date of introduction:  Never
 (Announced: May 26, 1982
 Cancelled: September 10, 1982)
Display technology:  
New price:  MSRP: $60.00 Display size:  
Size:  6.5" x 3.2" x 1.3"
 165 x 82 x 33 mm3
Printer technology:   
Weight:  7.4 ounces, 210 grams Serial No:  1235289
Batteries:  1*C Date of manufacture:  wk 56 (sic) year 1981
AC-Adapter:   Origin of manufacture:  USA (ATA)
Precision:   Integrated circuits:  TP0455/CD4511 or TP0456/CD4561, SN77203, LM393
Program steps:   Courtesy of:  Joerg Woerner

The CA-800 Cassette Interface allows to use most cassette audio recorders to save programs or data files on tape. It connects to the TI-88 Programmable through a 2-pin Peripheral I/O connector. A second Peripheral I/O connector on the back of the CA-800 allows to connect another device like the PC-800 Printer to the TI-88. The CA-800 is highly reliable because its redundant recording feature whereby information is stored twice no the tape.

The Operating System of the TI-88 supports four different types of tape recordings or tape files: 

Main memory file records all of calculator memory on tape
Program files from a minimum of eight program steps to all of program memory
Data files from a minimum of one data memory to all of data memory
Numbered Constant Memory Module (CRAM) records all contents of the module on tape

Dismantling this CA-800 manufactured most likely in April 1982 (Date code indicates week 56 of year 1981) by Texas Instruments in their Abilene, TX facility, reveals a rather complex design using a microcomputer of the TP0456 series and a SN77203 Voltage Controller chip together with some analog circuitry to connect to a tape recorder. The SN77203 is known from the TI-88 Schematics Diagram, it converts a single-cell battery (1.2 Volts - 1.5 Volts) to two independent power supplies, one adjustable for the LC-Display through a Serial I/O pin and one fixed for the main electronics. Due to the lower power consumption of its electronics is the battery life of the CA-800 projected to be 75 hour.

The TP0456 microcontroller sports Custom Design software CD4561, indicating that the original design was based on a TP0455 microcontroller with CD4511 software. Don't miss the CA-800 from an early DVT (Design Validation Test) Build featuring a translucent housing.

Color-coded plugs of the CA-800 to cassette audio recorder:

Black wire to remote jack
Red wire to microphone jack
Grey wire to earphone jack


Don't connect a CA-800 Cassette Interface or a PC-800 Printer to TI-88 calculators without the Diode-Modification!


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If you have additions to the above article please email:

Joerg Woerner, October 14, 2019. No reprints without written permission.