Pentica Mime-600

[Nick]

Dear community,

during my active business time in the period of 1980 / 1990 I developed SW in assembler using e.g. the above equipment. It was for the uC 68HC11. Later these years the unit was no longer used and it was almost scrapped, so I got it. It was working fine and I used it in my private home until 1995.

Some weeks ago I wanted to do some further assembler programming and debugging but the emulator does not respond to the activation via RS232 sending the character Ctrl-F.

Meanwhile after some weeks of measurement and analysis I am curious if someone else experienced the same behavior on this type of emulator.

I have checked:

- The oscillator of the controlling uP (MC68B09) is working fine and the NMI input is fed with a frequency of 123Hz (E clock divided by the IC CD4020)
- The character reaches the IC MC2681 on its RXD pin
- The EPROM content I have verified since a have a copy the original code ("Root")
- The rechargeable batterie has been replaced and I can measure 2,4V on several RAM chips when power is switched off.
- The power supply seems to be stable (+/- 5V, +/- 12V).

Does anybody of you has any idea that might help? Also I am desperately looking for schematics or a service manual for the emulator. Pentica Ltd. does no longer exist ....

Best regards

Nick

[joeqsmith]

I still have mine but have not turned it on in many years.   Last time I used it, I was designing this reverse Ethernet print server.  It emulates a Centronics port and allows my old TE to print to an Ethernet printer.    For this project, I upgraded my MIME to support a faster controller.   The poor thing is loaded with ceramic caps tacked to the boards to tame it.   Was very reliable after that.   

With it working at one time, I assume your sure the RS-232 cable is correct and the signally from the PC is correct.   I don't remember the upper BAUD rate it supported but wouldn't be surprised if it had trouble with a modern USB high speed adapter.   I've seen some crappy RS-232 adapters as well would not switch to the proper minimum levels.   If all the basics are there, not sure what to tell you.  I never had schematics for mine. 

[Nick]

Dear joeqsmith,

as I have told the Ctrl-F character reaches the MC2681 - but the emulator does not respond. The main controller on the upmost board (68B09) seems to work - but I doubt that it is using the correct code. With my Dreamsourcelab logic analyzer I tracked the initialization of the MC2681 (/WR, /RD, D0-7, RS 1-4, CS) but it seems to be not done! I will look further into the access of the EPROM and the RAM belonging to 68B09.

One question I have: could you check on your system whether the unit responds when the connection to the lower boards is not given?

Another question I have: is your Mime-600 as well for the 68HC11?

Best regards

Nick

[joeqsmith]

It supports two different flavors of the 11.