alister@asis.unimelb.EDU.AU (Alister Miller) (06/06/91)
I am having trouble using a modem with my A1000. When the modem is plugged in and turned on, every disk is 'corrupt', the drive light switches on and off in cycles of about 30sec (when no disk access is occuring), and the drive makes horrible noises when disk is being accessed. I am using a standard RS232 cable, with every line wired up. Do I need a special cable? P.S. What's the best PD modem program these days? Mine are ancient. Please respond if you know what's wrong, (E-mail preferred to save bandwidth). Alister Miller, University of Melbourne, Australia.
davem@col.hp.com (Dave K. Martin) (06/07/91)
I would suspect that the modem cable is causing your problems. There are some non standard signals present on the Amiga's serial port. Probably your modem is shorting one of the Amiga power outputs, +5 or +12 volts, to ground. The A-1000 power supply is robust enough to allow a short on one section (using a long length of small diameter wire) and still keep the computer operating. I don't have my Amiga hardware manual handy so I can't tell you which pins they are. Try using a different cable that only connects pins 2, 3, 4, 5, 6, 7, 8, 20 and 22. These should cover everything your modem wants. The RS in RS-232 stands for 'Recommended Standard' and virtually every manufacturer changes the pinouts on the lesser used pins for their own purposes. The A-1000 has some neat signals appearing on the serial port though.I can't remember them off the top of my head but I'm pretty sure that both sound channels are present along with the +5, +12 and -12 volt power sources. I'll probably hear from hundreds who have used a 25 line cable with no problems :-) . Actually, I've done it myself but only on a modem that left all of the pins that it didn't care about unterminated. Hope this is helpful............. davem
bj@cbmvax.commodore.com (Brian Jackson) (06/08/91)
In article <36000001@col.hp.com> davem@col.hp.com (Dave K. Martin) writes: >I would suspect that the modem cable is causing your problems. There are some >non standard signals present on the Amiga's serial port. Probably your modem >is shorting one of the Amiga power outputs, +5 or +12 volts, to ground. >The A-1000 power supply is robust enough to allow a short on one section (using >a long length of small diameter wire) and still keep the computer operating. > >I don't have my Amiga hardware manual handy so I can't tell you which pins they >are. Try using a different cable that only connects pins 2, 3, 4, 5, 6, 7, 8, >20 and 22. These should cover everything your modem wants. > >The RS in RS-232 stands for 'Recommended Standard' and virtually >every manufacturer changes the pinouts on the lesser used pins for their own >purposes. The A-1000 has some neat signals appearing on the serial port though. >I can't remember them off the top of my head but I'm pretty sure that both >sound channels are present along with the +5, +12 and -12 volt power sources. > ... >davem The 1989 Hardware manual says that the only serial pins that your modem should touch are pins 1-8, and 20. The especially dangerous ones are pins 14,21 and 23 (they are power sources.) On the A1000 pin 25 is a 'buffered system reset' which, if triggered by the modem, can/will reboot the machine. The Supra 2400 did it to mine; that's how I discovered that I had unwittingly switched cables to a 'standard' serial cable.) Brian ----------------------------------------------------------------------- | Brian Jackson Software Engineer, Commodore-Amiga Inc. GEnie: B.J. | | bj@cbmvax.cbm.commodore.com or ...{uunet|rutgers}!cbmvax!bj | -----------------------------------------------------------------------