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PMAC ISA conversion to serial communication
#1
We have a small stockpile of old PMAC Lite ISA cards that should work (I'm actually in the middle of testing them). These cards are mostly (or all) used cards that were returned from customers during troubleshooting or upgrades, and in most cases there is nothing wrong with the card. Since ISA capable PCs are so hard to find now, we are strongly considering mounting these cards on a homebrew backplane, and using RS-232 to communicate.

I have RS-232 communications working on the card on my bench, but I notice that the communication is almost unbearably slow. I removed the E45 and E46 jumpers to set the port speed to 38400, and have changed the port speed in the PCOMM32 settings, but the speed didn't really change.

When downloading a configuration to the card, if I choose YES to use checksums, I get a timeout during read of every 100th or so PVar. Is this normal with serial comms? Selecting NO to checksums doesn't give me this error, and the download is significantly faster.

Any help or past experiences are greatly appreciated.

-Ian
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#2
Hi Ian,
I don't know the expert or official answer to your question. But I have been using PMAC's for 10+ years and done 1000's of downloads, uploads using the serial ports. I NEVER use the checksum... and I have NEVER had a failure. I'm not sure how it is implemented in the PMAC software but it is so crippling that it has not use as far as I'm concerned.
I think the serial comms are fine for many applications that only require basic talking to the PMAC.
It is also possible to connect those PMAC's to PC104 bus type PC... these are still readily available and people who use them love them, I know several large machine builders that still use PC104 based systems. The PC104 backplane is same as ISA so it just works.

However my opinion the PMAC's are not worth much for new projects unless they are for your own machines then they are great, but to someone else who can buy a Clipper for $1000 why would they buy a old PMAC ISA that may not even be repairable if it breaks ?

They are however worth a lot on the market for existing PMAC PC users... they can get $1000 - $3000 easily.
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#3
Hi Ian,

Non-Turbo PMACs' serial speed varies greatly from board to board. For older boards, the default speed is 9600 baudrate. For newer boards including most of PMAC lite boards the default speed is 38400, but speed really depends on CPU type, speed, and jumper settings.

PMAC ISA and PMAC PC104 are identical as far as serial communication is concerned. PC104 is essentially an ISA bus. The difference is that PMAC PC104 is set at 38400 baudrat as default. PMAC lite with Flex CPU are also set at 38400 as default while for older boards serial speed is set at 9600 and is adjusted by jumpers as opposed to I variables.

In Pewin32Pro and Pewin32Pro2 serial communication is optimally configured at 38400 baudrate and should work fine both with and without checksum. If you have the exact specification then call our customer support or any of software person and we will be able to help solve serial comm. problem.

Farooq
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#4
(10-22-2010, 10:13 AM)fahmad Wrote: Hi Ian,

Non-Turbo PMACs' serial speed varies greatly from board to board. For older boards, the default speed is 9600 baudrate. For newer boards including most of PMAC lite boards the default speed is 38400, but speed really depends on CPU type, speed, and jumper settings.

PMAC ISA and PMAC PC104 are identical as far as serial communication is concerned. PC104 is essentially an ISA bus. The difference is that PMAC PC104 is set at 38400 baudrat as default. PMAC lite with Flex CPU are also set at 38400 as default while for older boards serial speed is set at 9600 and is adjusted by jumpers as opposed to I variables.

In Pewin32Pro and Pewin32Pro2 serial communication is optimally configured at 38400 baudrate and should work fine both with and without checksum. If you have the exact specification then call our customer support or any of software person and we will be able to help solve serial comm. problem.

Farooq

Farooq,

Thanks for responding. I have set the card(s) to 38400, and I get reasonable communication to the card(s). Even set this way, I still get timeouts sometimes. I have the timeout set to 3500ms; is this good enough? 3500ms seems like a large timeout period.

We are using LabVIEW to communicate to the cards (PMAC Panel Pro 2.0). We just want to know if the serial port will be fast enough to switch over to using serial comms on these older cards in our application. We have several, and they are worth a lot to our customers (many machines dating from the early 2000s), so we hate to end up throwing them away.

I expect the ISA bus to be faster, but can you give me any kind of "maximum amount of commands per second" or something similar for RS-232 versus ISA or PCI?
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