My try to have a Sigrok based decoder for signals from the venerable pocket calculators made by texas Instruments.
Useful signals: 4 bit data bus, IDLE, EXT, IRG, PHI1.
Some signals are available at the library module slot:
- IDLE, EXT, IRG, PHI1
- GND (I use Vdd for that together with my KingST LA5032 Logic Analyzer)
4 bit data bus is only available at the chip pins after removing the back of the TI housing.
Two example view of some early version of the decoder. Several instruction cycles are shown. LA was used with 1 MS/sec and 5 MS/sec.
On startup, sigrok and pulseview look in several directories for decoders.
On Linux for example, the local user directory that can contain custom
decoders is located at $HOME/.local/share/libsigrokdecode/decoders
Check Pulseview/Sigrok documentation for required location on other operating
systems.
Create a new directory ti5x in the mentioned directory and copy all files
from this repository to that directory, e.g. into $HOME/.local/share/libsigrokdecode/decoders/ti5x
(Absolutely required files are: init.py and pd.py)
After installation part described avove, restart Pulseview.
It should now offer the new decoder in the decoder section "Retro computing".
If you have named the Pins 0..7 with correct names (IDLE, EXT, IRG, IO8, IO4, IO2, IO1, PHI1), Pulseview will connect these pins directly to the decoder inputs and decoding will start.
In directory examples I've put two sigrok sample data dumps. These can
be loaded by pulseview, the decoder then can be applied to them.
-
examples/ti59-session001-4secs-5mhz-switch-on.*: This is a sample with length of 4 seconds from a well working TI-59. 5Mhz sample rate.
The TI-59 is being switched on. What can be seen in the sample is that the calculator does some initialization stuff, IDLE signal is in "CALCULATE" mode. After initialization, the calculator goes to "DISPLAY" mode, waiting for key presses.
-
examples/ti58c-session000-5secs-switch-on-auswahl.*: This is a sample of about 5 seconds from a broken TI-58C. 1Mhz sample rate.
The TI-58C is being switched on. There is also an initialization section in CALCULATE mode and then the section where calculator seems to wait for key presses, then in DISPLAY mode. The calculator is broken, does not respond to key presses and displays arbitrary random data in display.
Note: For both samples, the GND pin of the logic analyzer used was attached to Vdd. This was done because if being connected to calculators Vss (0 volts), the signals could not be detected. The Signals are PMOS and run between 0 volts(=Vss) and -15.6(=Vgg) / -10 volts (=Vdd). These values are too large for my logic analyzer KingST LA5032, which has maximum LO/HI threshold of +4 .. -4 volts. So I have used Vdd as "virtual GND" to take these samples. This should not lead to issues, but see TODOs section below.
| Signal | Level related to Vss | Level related to Vdd |
|---|---|---|
| PHI1 | HI=0V, LO=-15.6V | HI=10V, LO=-5.6V |
| IDLE | HI=0V, LO=-10V | HI=10V, LO=0V |
| IRG | Like IDLE | Like IDLE |
| IO* | Like IDLE | Like IDLE |
- IO-lines processing not yet done
- I am not sure at all that the decoding works correct. For example, the IO lines show activity after all BRA (branch) instructions (seems ok), but also after many other instructions, which does not make sense to me. Notably, IO line activity can be seen after/during mask operations (like .MANT etc.), which looks strange to me.
- Calculators TI–58/59 HW programming guide, by Hynek Sladky. This document contains a large bunch of valuable information and also instruction code tables
- TI PC-100A Interface Description. Original document by Texas Instruments from 1978. Explains software/hardware protocol in detail, with focus on printer cradle.
- 4153937 "Microprocessor system having high order capability", 1977
All patents that had been used by Texas Instruments are listed here: http://www.datamath.org/Patents.htm