smaller HP 82166A with 32-pin connector

[KimH]

The idea of connecting the Plotter as you have done here - or even a RAM block - is now on my list, once it starts raining again.

Cool inspiration, thank you for that!

Have you tried working with the TRIGGER command and the GETO-line on the interface? My fist couple of attempts controlling Inputs from the 165A with a TRIGGER did not yield anything sensible. On top the documentation I can find regarding TRIGGER/GETO is not exactly great.

Any ideas are welcome!

(09-06-2021 07:37 AM)Klaus Overhage Wrote:  Actually, this byte should also be available some time before and after the strobe, but the HP 82165 as well as the HP 82166A switch the 8 data lines to high resistance (TRISTATE) immediately after setting the strobe line high again, which is read by the X-710 as 255. Inverting the strobe line did not help either, nor did an extension of the DAVO signal with the help of registers R02 and R03 of the HP devices.

With an old 2-channel oscilloscope, I was able to track the temporal relationships and also see that the X-710 briefly sets its BUSY output to high to confirm the data transfer. I have come to the conclusion that the X-710 needs more time to take over the data after the strobe. With the help of the circuitry shown above from the two IC'S 74HCT573 and 4069, the data byte is now buffered. The STROBE signal goes directly to the plotter and is inverted for the LE input of the 74HCT573 using the 4069.

The BUSY output of the plotter goes directly to the RDYI input of the HP-82166A. However, the X-710 cannot pull the RDYI input to low. I had to install a 1k Ohm resistor from RDYI to GND so that the BUSY signal was recognized. The 5V supply voltage for the two ICs and the HP 82166A is generated by a WINOMO LM2596S LM2577S DC-DC converter from the battery voltage (6.2V) provided by the X-710.

Now everything works, as the linked video shows.
https://www.dropbox.com/s/n359qnu6ypsnus...M.mp4?dl=0