Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uflorida!gatech!udel!udccvax1!gdtltr
From: gdtltr@vax1.acs.udel.EDU (Gary D Duzan)
Newsgroups: comp.sys.atari.8bit
Subject: Re: Parallel Printer interface
Message-ID: <3265@udccvax1.acs.udel.EDU>
Date: 8 Apr 89 00:00:00 GMT
References: <8904071504.AA22717@ucbvax.Berkeley.EDU> <682@orchid.waterloo.edu>
Reply-To: gdtltr@vax1.acs.udel.EDU (Gary D Duzan)
Organization: Galadrim (really a disorganization)
Lines: 48

In article <682@orchid.waterloo.edu> rbharding@orchid.waterloo.edu (Ron Harding) writes:
>
>   I was wondering about how Atari printer interfaces, or the P: driver handle
>conversion of ATASCII to ASCII.  It seems to me that if the ATASCII codes such
>as EOL (155, $9b) are universally converted to the ASCII codes, such as CR/LF
>(13,10 $0d$0a), then important things like dot-matrix graphics will be munged
>up.  But if they aren't converted, then normal text won't print properly.
>
>   How is this resolved?  My theory is the following:
>
   In general, this is handled by the interface. ALL EOL's (155) are
translated into CR (13, or CR/LF (13/10), depending on the interface.) This
does, in fact, disallow code 155 in any bit-mapped output to the printer.
Generally, programs which send bit-mapped data to the printer are required to
check for a 155 and either report an error or send it varied slightly (more
likely the former.)

>- The P: handler will perform conversion of ATASCII to ASCII if the output
>command is PUT_RECORD.  This command is line-oriented (a record is always
>terminated by an ATASCII EOL (155) ).
>
>- If the output command is a PUT_BYTES, the P: handler performs no conversion
>whatsoever, so graphics dumps will work correctly.
>
>   Am I reasonably close to the truth here?  I need to know, since I am faced 
>with the task of writing a P: driver for the parallel port I built for my old-
>style 800.  Currently, I use a cludgy SpartaDOS program I whipped up:
>      PPRINT fname.ext
>
   For a general solution, rewriting (or patching) the built-in P:
handler to change all 155's to 13's (or 13/10's) would be best. "Mapping
the Atari", Codebuster, your favorite assembler, and a good bit of stamina
would be all you would really need (assuming a working knowledge of the
Atari OS & the 6502.) I would advise against your above suggestions due
to possible problems with compatability. Your best bet would be to write
a general PUT_BYTE routine that does the conversion and have PUT_RECORD
and PUT_BLOCK call PUT_BYTE directly for each character.


>   Thanks in advance.
>
>                                Ron Harding
   You are certainly welcome.

					Gary Duzan
					Time  Lord
				    Third Regeneration
				 Atari Enthusiast Extreme