edp@jareth.enet.dec.com (Eric Postpischil (Always mount a scratch monkey.)) (04/10/91)
Has anybody used the HP-48 with a modem? The 48 controls the Transmit Data line but apparently leaves the Ready To Send and Data Terminal Ready lines unchanged. And it seems the modem expects Ready To Send and Data Terminal Ready to be asserted -- and their polarity is different from that for Transmit Data, which makes me think asserting RTS and DTR can't be done just with a couple of jumpers. Are there any solutions? -- edp (Eric Postpischil) "Always mount a scratch monkey." edp@jareth.enet.dec.com
steveh@hpcvra.cv.hp.com. (Steve Harper) (04/11/91)
Modems are a variable lot ... But they normally do expect to have their RTS (request to send) and DTR (data terminal ready) lines asserted (>3V or so). The HP 48 doesn't have these signals. It implements only a simple "3-wire" serial interface (transmit data, receive data, and signal ground). Most modems have either hardware or software configuration switches that tell the modem to ignore (or not to ignore) the state of these handshake lines (RTS, DTR). How these switches are twiddled varies widely depending on the model and manufacturer of the modem. If you set your modem configuration to ignore the state of the handshake lines, it should work just fine with the HP 48... Good luck! Steve
robert@longs.LANCE.ColoState.Edu (04/12/91)
*> Has anybody used the HP-48 with a modem? The 48 controls the Transmit *> Data line but apparently leaves the Ready To Send and Data Terminal *> Ready lines unchanged. And it seems the modem expects Ready To Send and *> Data Terminal Ready to be asserted -- and their polarity is different *> from that for Transmit Data, which makes me think asserting RTS and DTR *> can't be done just with a couple of jumpers. Are there any solutions? *> *> *> -- edp (Eric Postpischil) *> "Always mount a scratch monkey." *> edp@jareth.enet.dec.com I use my 48 with a modem quite frequently. I makes for good kermit transfers to and from the host easy :-) All I did was get a straight through cable and then (on the modem end) jumper pins 6 and 20 and also jumper 4 and 5. Everything else works just fine. Hope this helps... -Robert
lishka@uwslh.slh.wisc.edu (a.k.a. Chri) (04/12/91)
edp@jareth.enet.dec.com (Eric Postpischil (Always mount a scratch monkey.)) writes: >Has anybody used the HP-48 with a modem? The 48 controls the Transmit >Data line but apparently leaves the Ready To Send and Data Terminal >Ready lines unchanged. I don't see how the hp48sx could ever deal with RTS and DTR because it only has send, transmit, and ground lines. Of course, hardware mods might be able to get it to work, but that seems silly. >And it seems the modem expects Ready To Send and >Data Terminal Ready to be asserted -- and their polarity is different >from that for Transmit Data, which makes me think asserting RTS and DTR >can't be done just with a couple of jumpers. Are there any solutions? "We have ways of making modems talk!" Some modems allow for DTR and RTS to be ignored. There are also ways to jumper RS232 lines together to "fool" the modem into thinking it received the DTR signal. I believe some terminals and/or PC's use only send/transmit/ground to talk to peripherals with success. Find a good RS232 guru. Unfortunately, I am not a hardware type and it has been too long since I tricked my old Teleray terminal into thinking DTR was connected to the modem when it wasn't. .oO Chris Oo. -- Christopher Lishka 608-262-4485 It is not safe out here. It is wonderous, Wisconsin State Lab. of Hygiene with treasures to satiate desires both lishka@uwslh.slh.wisc.edu subtle and gross. But it is not for the uunet!uwvax!uwslh!lishka timid. -- Q
EBERBERS%yubgef51@pucc.PRINCETON.EDU (____ Zarko Berberski ____) (04/13/91)
> And it seems the modem expects Ready To Send and > Data Terminal Ready to be asserted -- If HP-48 can communicate with computer with just TD/RD lines then it can do the same with a modem. RTS/CTS is somethimes used by some used by some communication software (and even in some low-level OS routines) but modem doesn't need it. Same applies to DTR but this signal is much more important and you must use a micro-switch on your modem to force it to ignore DTR. If you by any chance have so sophisticated modem (with internal buffers, different in/out speed etc..) that can't live without RTS/CTS then there must be a switch for this too. The general rule is - you can always make modem as dumb as you like. But - you have to connect HP's TD to modem's RD and vice versa (since modem and HP port are the same "type" of device). Zarko Berberski EBERBERS@YUBGEF51.bitnet