biswa@ohm.berkeley.edu (Biswa Ranjan Ghosh) (01/16/91)
On the subject of substituting other cables for Appletalk cables: >>>2. I have been told by a usually reliable source (MacConnection) that you >>> can hook a single Mac up to a single AppleTalk device (e.g, a non-SC >>> LaserWriter) with an ImageWriter cable, with the implication that >>> somehow the wires are right for a two node AppleTalk network. Is this >>> correct? Apple of course says to buy two AppleTalk connector kits. > And in a different article, >No, you can really use an ImageWriter II cable in a two node network. I have >an Imagewriter 2 and an SE/30, and have an appletalk card in the printer for >reasons that I'm sure you don't care about. I use a stock IW2 cable and it >works fine (and has for quite some time now). > O.K., now I'm confused. I really want to hook up my SE/30 directly to our Apple Laserwriter in the lab directly, without plunking down money for an Appletalk cable. Problem is, the laserwriter has only a 9-pin socket and a 25-pin socket, neither of which is the 8-pin mini-din that is on both ends of an IW-II cable. So how is it done? Also, the laserwriter has a knob by the sockets, with selections: Appletalk, Special, 9600, 1200. Which of the four should be used? Here is some info quoted directly from the Apple Laserwriter manual: (Appendix C, pg 124) Pin Assignments The signal pin assignments for the 9-pin (RS-422) connector are: 3 Signal ground 4 Transmit data + 5 Transmit data - 8 Receive data + 9 Receive data - This pin assignment is compatible with the Macintosh; therefore, it's possible to connect a LaserWriter directly to a Macintosh using an Apple Modem cable and to communicate with it using MacTerminal. The signal pin assignments for the 25-pin (RS-232) connector are: 2 Transmit data 3 Receiver data 4 Request to send (optional; needed only if host requires it) 7 Signal ground 20 Data Terminal Ready (optional) >My note: That last one looks like a typo, there should be a carriage return > after the Signal ground. The other signals are not used. Technically, the LaserWriter has a "DTE" type of RS-232 interface. THis means it can be connected directly to a host computer or a modem, with no signal reversals required. Connecting to a terminal requires interposing a modem eliminator (null modem) cable, which at a minimum involves reversing the transmit data and receive data signals. The Mode Switch The mode switch is preset at the AppleTalk position. As long as you use the AppleTalk connector attached to the 9-pin socket, you won't change this switch. The other positions are used as follow: * Special - 1) Makes the printer emulate a Diablo 630 printer when a device is connected to the 25-pin socket; 2) sends PostScript, the LaserWriter's programming language, back and forth between MacTerminal and the Laserwriter. * 9600 or 1200 - preset baud rates for RS-232/422 communication with either the 9-pin or 25-pin serial connector. **** end of quote **** Now here's what I don't understand. According to the manual, seems I should get an Apple modem cable. But it also says I have to communicate with the laserwriter using MacTerminal, and should set the mode switch to Special. But what I *really* want to do is just choose the laserwriter in the Chooser as if it were on an Appletalk network, and print. Don't want to worry about using some modem program like MacTerminal. So, since I certainly don't want to damage someone else's laserwriter, can anyone tell me, 1) What cable should I use? Has to be RS-422 or RS-232 on one end. I can construct my own if I am told the pin assignments on both ends. 2) What should the mode switch be set to? I hope Appletalk. 3) Would the method of printing be the standard one, i.e., choose laserwriter from chooser and issue print commands from my favorite wordprocessor pgm? Biswa Ghosh 550 Cory Hall arpa: biswa@janus.berkeley.edu U.C. Berkeley uucp: ...ucbvax!janus!biswa Berkeley, CA 94720 tel: (415) 642-0395