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PC link to 8051 Mode 2/3: Multiprocessor Serial Bus

Cross-posting from the 8052.com forum http://www.8052.com/forum/index.phtml

A while back (http://www.8052.com/forum/read.phtml?id=23083), I asked about how to get a PC to read the 9th bit in Mode 2/3: Multiprocessor Serial bus format.

I need to be able to detect the state of the 9th bit for each received byte.

Mahmood Elnasser suggested the cport library: http://www2.arnes.si/~sopecrni/downloads/CPort263.zip

I've downloaded this, and it doesn't look like it'll do the job :-(
(It looks like it'll have the same problem as AsyncPro)

The OnRxChar Event could return any number of characters, but the LastErrors Method - as its name suggests - only tells me what the last error was; ie, I can't tell which of the received bytes had the 9th bit set (Parity error).

Any help would be greatly appreciated.

I'm currently looking around at direct IO drivers for Windows

(yes, I know it'd be a doddle in MS-DOS).

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  • Thanks Jon

    Their COMM-DRV.VxD page does indeed mention "With one call the first byte is sent with 9 bits while the others are transmitted normally."
    http://www.wcscnet.com/CdrvVBro.htm

    But this is not quite what I want: I need all bytes transmitted with 9 bits, and b9 is set for "special" bytes and clear for "normal" bytes:
    From the bus Master, b9 set indicates an address byte (at the start of a message);
    From a Slave, b9 set marks the last byte of a response.

    Have you actually used any of their products?
    What was your opinion?

  • I had to support some multiport UARTS several years ago (before the 9 bit support was added). I used the LIB product. It worked flawlessly, and was well documented.

    With a little work, I am thinking you might be able to translate the 9'th bit as address to a 9'th bit as end of packet indicator. Definitely worth a Email to ask them.

  • Yes, they say it has a "StoreAll" mode in which data & status are queued together

    It certainly looks worth a try!