Path: utzoo!mnetor!uunet!lll-winken!lll-tis!ames!ucsd!sdcsvax!ucsdhub!hp-sdd!ncr-sd!ncrlnk!adds!kieran
From: kieran@adds.newyork.NCR.COM (Joe Cabana)
Newsgroups: comp.sys.m6809
Subject: Re: Problems with /t2 & /t3, hardware not software
Message-ID: <564@adds.newyork.NCR.COM>
Date: 7 Apr 88 20:35:15 GMT
References: <4757@pucc.Princeton.EDU> <2617@tekgen.TEK.COM> <494@flatline.UUCP>
Reply-To: kieran@adds.newyork.NCR.COM (Joe Cabana)
Organization: Applied Digital Data Systems, Hauppauge N.Y.
Lines: 26
Summary: Can't do it.

In article <494@flatline.UUCP> phaedrus@flatline.UUCP (james hartman) writes:
>In article <2617@tekgen.TEK.COM>, jonh@tekgen.TEK.COM (Jon Howell) writes:
>
>[Description of data going out to one pak going to both on his L2 system]
>
>As with the 300bps modem pack drivers (/m1 and /m2), /t2 and /t3 cannot be
>used at the same time.  Why?  They both use the ACIApak driver under L2, so
>any data that goes out to either one is run through that driver.  The only
>difference between /t2 and /t3 is which slot of the MPI the RS-232 is in
>(since 1 and 4 have the hardware support for interrupts and slots 2 and 3
>do not).  This, unfortunately, is a silly oversight on the part of the Shack
>and/or Microware.  [This information is taken from the old L1 update package
>that was put out before the CC3 for various compatibility reasons.]
>

Actually the reason characters appear on both ports is because of a hardware
limitation in the RS-232 packs themselves, not a software problem.
If you look at the schematics in the RS-232 pack tech. ref. manual you'll find
the RS-232 packs are setup to use the slot select lines to enable thier ROMS
but NOT the UARTS. This means that no matter what slot you put the pack in,
the UART will always be at the same address. There is no way to put two
RS-232 packs in at once without hardware mods to change the address of one
pack and software changes to use the new address. The reason for two
drivers (as far as I can tell) is to allow you a choice of slots in
case of conflict. (OS-9 still needs to know which slot has the ROM).

              J. E. Cabana kieran@adds.newyork.NCR.COM