gil@limbic.UUCP (Gil Kloepfer Jr.) (05/02/88)
In article <4588@ihlpf.ATT.COM> gmark@ihlpf.ATT.COM (Stewart) writes: |>This is an unusual request, I think: Is it possible to configure the |>EIA ports on a UNIX-PC (EIA/RAM Combo board) such that they allow |>data to just pass through from a device on one side to a device on the |>other as though the two were directly connected? And then to make this |>pass-through configuration switchable to "normal" (EIA to a modem or some |>such) via software? ALL information would be appreciated. |> |> G. Mark Stewart |> ATT-BTL Naperville, ix1g266 |> ixlpq!gms 979-0914 (Thanks to Lenny Tropiano for letting me examine his EIA board and some other stuff) Some interesting information about the EIA/RAM board. The EIA/RS232 ports that are there are controlled by a Z8530 SCC chip (this is a Zilog Serial Communications Controller chip, part of the Z8000 series support chips). What's even more interesting is what is contained in /usr/include/sys/i8274.h. Essentially, the Intel 8274 SCC is a subset of the Z8530, and the 8274 is the beast that is inside the UNIX-PC that controls the serial port and built-in modem that comes with the base 3B1 (7300). To answer the question posed above, the answer is no. There is no configuration of the Z8530 (that I can see in the specs) that would allow you to connect channel A to channel B (the designations for the individual I/O channels in the Z8530 specs) since they are independent of one another. You would need software which esentially reads the character from the respective channel and writes the character to the other channel. I can imagine what this would do to the speed of anything else executing at the time when the baud rates on the ports were high! ---- Now a question to add to this answer --- how does one directly access the hardware on the UNIX-PC? I would like to know how I bypass the OS completely (as though I never had a device driver attached to, say, the i8274 which controls the serial port & built-in modem). Are there any docs (aside from the .h files) which I could obtain which would explain the locations in some kind of detail? And how do I address hardware directly from C? Someone has my 68000 series books, so my next question is: Are the hardware devices memory-mapped, or are there special I/O addresses for these (like in the Z-80 and 8080 MPU's)? Any help with this would also be appreciated. +------------------------------------+----------------------------------------+ | Gil Kloepfer, Jr. | Net-Address: | | ICUS Computer Group, Systems Dvlp. | {boulder,ihnp4,talcott}!icus!limbic!gil| | P.O. Box 1 | Voice-net: (516) 968-6860 | | Islip Terrace, New York 11752 | Othernet: limbic!gil@icus.UUCP | +------------------------------------+----------------------------------------+