kujanpa@ccu.umanitoba.ca (12/11/90)
Hi everyone. Here's my problem: Besides our ethernet, we have a packet switching network (Develnet). This network provides 9600 baud ASCII serial ports to the mainframe for pc users. The problem comes when we connect a Mac to one of these ports. They will occasionally lockup to a point, where a linecard has to be pulled and reset. I think the problem comes from the Mac (RS-422?) talking to RS-232. All we use is a modified cable to emulate RS-232. Over long distances the voltage level coming out of the Mac is very small (ie. not valid data). The question: Can I build a circuit to change from RS-422 to RS-232? Can this circuit be powered from the Mac SE port? Using an external power supply is ok, but if the circuit could be powered from the line it would be great. Any suggestions, ideas, etc. are more than welcome! Thanks in advance! Bob Kujanpaa kujanpa@ccu.UManitoba.CA Any suggestion
touch@dsl.cis.upenn.edu (Joe Touch) (12/11/90)
In article <1990Dec10.173757.1162@ccu.umanitoba.ca> kujanpa@ccu.umanitoba.ca writes: > >I think the problem comes from the Mac (RS-422?) >talking to RS-232. All we use is a modified cable >to emulate RS-232. Over long distances the voltage ^^^^^^^^^^^^^^ >level coming out of the Mac is very small (ie. not The first problem isn't the MAC, its the RS232. RS232 is designed to go over less than about 30 yards or so. RS422 is a balanced-pair differential, which IS capable of going further. Joe
tom@bumrl1.bu.edu (Tomislav Lozic) (12/11/90)
In article <1990Dec10.173757.1162@ccu.umanitoba.ca>, kujanpa@ccu.umanitoba.ca writes: |> |> Can I build a circuit to change from RS-422 to RS-232? |> Can this circuit be powered from the Mac SE port? |> Using an external power supply is ok, but if the |> circuit could be powered from the line it would be |> great. |> You _can_ build such a circuit. However, if you have better things to do, you can buy RS-232 to RS-422 converter for about $10-$15 from B&B electronics. Their address is: B&B electronics P.O.Box 1040 Ottawa, Illinois 61350 The part is: RS-232 to RS-422 converter (model 422CFC) It comes together with a required power-supply (12V, 100mA). [ I don't know of any such circuit that is powered from SI port ] NOTE: To have a good long-distance performance connect the converter at RS-232 side and use RS-422 cable. (More expensive but also more reliable than long RS-232 cable.) ___________________________________ Tomislav Lozic <tom@bumrl1.bu.edu>