[net.micro.cpm] MODEM730 & KAYPRO: can't print to Epson

kemp@noscvax.UUCP (06/04/84)

Help!
  I'm using MODEM730 on a Kaypro 4 (old, purchased Oct. 83) with a 300 baud
modem, and an Epson MX80 printer with GrafTrax running through the serial
port.
  The MODEM730 was derived from M7KP-1.ASM and installed to know about
the Hayes Smartmodem (even though I'm not running from one). I created the
COM file from SIMTEL20's HEX file, and installed by using DDT.
  My host is a VAX 11/780 running 4.2bsd Unix.

********* the problem *********
  When I select ^P to toggle the Epson online, subsequent lines are losing
characters both on the screen and at the printer. It looks like usually the
missing characters are at the left part of the lines.
  When I toggle the printer off, characters stop disappearing.

  What have I done wrong? I also saw this behavior in earlier versions of
MODEM7, so I don't think the problem is a new one.

  Any ideas?   Thanks in advance!

      Steve Kemp
      Computer Sciences Corp.
      Naval Ocean Systems Center
      San Diego, CA

      kemp@nosc
        -or-
      ...ucbvax!sdcsvax!noscvax!kemp

jwc@edison.UUCP (07/06/84)

Steve, the trouble you're having is due to a bug in the Kaypro BIOS and ROM.
According to the DRI manuals, BIOS call 14 (LISTST) should return a zero in A
if the printer is ready, and an FF if it is not. Kaypro sets the zero FLAG,
but does not return a zero. Their LIST call checks the flag, so it works fine
for them. But MODEM7 et al checks for the contents of A, not the zero flag.
	There are two fixes:
1) Patch MDM7xx to get rid of the ANA A which sets the flag after the call to
the BIOS.
or
2) Patch the BIOS. This is about a six-byte patch, replacing the BIOS jump
vector with a jump to a free area, which contains:
			CALL LISTST
		RNZ
		XRA A
		RET.
If you have access to Compuserve, there's a complete patch in CP-MIG XA1.
I understand it is also on the Detroit TRCM.