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From: dwv%cadnet@UMIX.CC.UMICH.EDU (Doug Vander Wilt)
Newsgroups: comp.sys.apollo
Subject: Re: serial port splitter
Message-ID: <9106181716.AA07976@cadnet.micro.honeywell.com>
Date: 18 Jun 91 17:16:06 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 70

From last week, gary@osccsg.UUCP (Gary Smith) writes:
> 	I am trying to get a hold of the 3-way serial port splitter for a 
> Apollo 3550 unit.  Would anyone have descriptions on building a cable for
> this.  At this time work is unable to justify paying CDN$407 for such a 
> cable.

Well, I just verified some old notes I had on this subject.  It's relaxing,
once in a while, to just hide in the lab a few minutes to check continuity
on a cable.  This information is not guaranteed correct, but here's how the
port expander (or "Multiple Serial Connector") is wired:

    Apollo Serial Port Expander:
      - Expands single DB25Female serial port to 3
      - For use with:
        Apollo DN2500,3500,4000,4500
        HP/Apollo 9000 series 400
      - List price: K1015 $129
        (1990 No. 1, "Instant Apollo" Catalog)

    Cable Connections:
        DB25Male    RS232 sgnl  Expanded (3 * DB25Female)
        ----------- ----------- ----------- 
        1           SG--        SG1, SG2, SG3
        2           TD->        TD1
        3           RD<-        RD1
        4           RTS->       RTS1
        5           CTS<-       CTS1
        6           DSR<-
        7           GND--       GND1, GND2, GND3
        8           DCD<-       CD1
        9           +V          RD3
        10          -V          CTS3
        11
        12          S_RDTCT<-   TD2
        13          S_CTS<-     RD2
        14          S_TD->      RTS2
        15          DCE_CLK<-   CTS2
        16          S_RD<-      CD2
        17          RSET
        18                      DTR2
        19          S_RTS->     DTR3
        20          DTR->       DTR1
        21          SQUAL       TD3
        22          RI<-
        23          DRATE->     RTS3
        24          DTE_CLK->
        25                      CD3

    Signal definitions:
        SG      shield ground
        TD      transmit data
        RD      receive data
        RTS     request to send
        CTS     clear to send
        GND     signal ground
        CD      carrier detect
        DTR     data terminal ready

Entrepreneurial Opportunity!
    There may be a market for a DB25 to 3 * RJ11 style connectors instead of
using the port expander.  Then we could use readily available modular
connectors, and hopefully save some money.  The problem here is that I have
never seen any standard way to run serial comm. across RJ cable.  Danford
uses this on their SEU-3400 4-serial-port AT board for Apollo.  Does anyone
know of another established standard?

Doug Vander Wilt
Sr. CAD/CAM Engineer
Honeywell MICRO SWITCH Division
dwv@cadnet.micro.honeywell.com