TI-8x Graphing Calculators

The TI-8x series graphing calculators from Texas Instruments are powered by a derivative of Zilog's Z-80 microprocessor (except the TI-89). There exists a cadre of aficionados creating games and programs both in TI basic and Z-80 assembly language. TICALC is a good place to start your snoop.

TI-8x calculators also connect to TI Calculator-Based Laboratory (CBL and CBL2) modules. Data probes from TI and Vernier can be used to measure pH, dissolved oxygen, temperature, etc.

TI makes a Graph-Link cable and software to allow communication between a TI calculator and a PC or Mac.

Programs

I've written these programs to provide a more robust CBL connection.

• Capture single readings from the CBL. A text copy of capture.
• Dgraf gathers CBL data approx. every second and allows graphing. A text copy of dgraf.
• Dgraf uses a CBL checking program you will want to download also. A text copy of cblchk.

TI Graph Link Communication Reference Websites

The sites below provide complete and likely accurate background on the TI Graph Link Communication Protocol.

• Paul Singer's OSU site.
• TiLP is an open-source software project for PC to TI communication.
• Some work I have done with the protocol hardware layer.
  1. Normally both devices (TI-Calc and PC) monitor the signal lines for activity.
  2. To begin communication, a device brings one of the signal lines low. Either the TI-Calc or the PC can drop a signal line and either signal line can be brought low. The device dropping the first line is the Master and will control further communication.
  3. The device on the other end (the Slave) drops the line the Master did not control.
  4. If the Master drops the "1" line the first bit it is sending is a "1"
  5. If the Master drops the "0" line the first bit it is sending is a "0"
  6. After changing the state of a signal line, a device waits for the other device to acknowledge on the other signal line. Failure to do so causes a time-out error. The time-out interval is long enough for either device to service interrupts or higher priority tasks.  Nice.
  7. Timing Diagram (eight bit, no parity)
      
     
  teca_83i.htm   |  revised 8/25/2003