1. This forum section is a read-only archive which contains old newsgroup posts. If you wish to post a query, please do so in one of our main forum sections (here). This way you will get a faster, better response from the members on Motherboard Point.

Serial cross over cable and null modem cable

Discussion in 'PC Hardware' started by mydejamail, Apr 23, 2006.

  1. mydejamail

    mydejamail Guest

    Is a null modem cable different from a serial crossover cable?

    I am into a project that calls for a serial crossover cable, and I'd
    like to now what types of crossover cables they are?

    The connection is wired like this. The 1,6,8 are linked together and
    connected with 4 on the other side and vice versa. 7 on both sides is
    unused.

    2 - 3
    3 - 2
    5 - 5
    1
    6 - 4
    8
    1
    4 - 6
    8



    Does this type of linkage have some sort of classification?
     
    mydejamail, Apr 23, 2006
    #1
    1. Advertisements

  2. I'm no expert by a longshot, but...

    Here's some "null modem" and "serial crossover" charts I've saved
    from different web sites over the years. They look the same to me,
    other than your missing 7, and 4-to-8, vs their 7+8 crossed.

    ============================-

    Crossover pinout DB-9 serial cable

    pin signal pin signal
    1 CD 4 DTR
    2 RD 3 TD
    3 TD 2 RD
    4 DTR 1 CD
    4 DTR 6 DSR
    5 SG 5 SG
    6 DSR 4 DTR
    7 RTS 8 CTS
    8 CTS 7 RTS

    ===========================
    Null-Modem Pinouts DB-9 to DB-9

    1 and 6 to 4
    2 to 3
    3 to 2
    4 to 1 and 6
    5 to 5
    7 to 8
    8 to 7

    =========================
    (Slightly modified chart from Microsoft)
    http://support.microsoft.com/kb/q142324/

    This section describes the wiring specifications for serial InterLink
    cables that can be used with Direct Cable Connection. To make a
    serial InterLink cable, make a serial cable with either a 9-pin or
    25-pin female connector on both ends, and wire the cable as follows:

    9-pin 9-pin Description
    ----------------------------------------------------------------------
    pin 5 <------> pin 5 Ground-Ground
    pin 3 <------> pin 2 Xmit-Rcv
    pin 7 <------> pin 8 RTS-CTS
    pin 1 and 6<------> pin 4 DSR-DTR
    pin 2 <------> pin 3 Xmit-Rcv
    pin 8 <------> pn 7 CTS-RTS
    pin 4 <------> pin 1 and 6 DTR-DSR

    ====================================
     
    MasterBlaster, Apr 24, 2006
    #2
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.