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From: rhealey@ub.d.umn.edu (Rob Healey)
Newsgroups: comp.sys.tandy
Subject: Re: TRS-80 Model 4P info
Message-ID: <141@ub.d.umn.edu>
Date: 22 Jul 90 03:54:59 GMT
References: <34219@ut-emx.UUCP> <1990Jul19.212039.10680@techbook.com>
Distribution: usa
Organization: University of Minnesota, Duluth. Information Services.
Lines: 28

In article <1990Jul19.212039.10680@techbook.com> fzsitvay@techbook.com (Frank Zsitvay) writes:
>>I need some technical info on the trs-80 model 4 P, the portable
>>version of the model 4.  I'm interested primarily in the video and
>>keyboard circuitry and software.  Can anyone point me to a source?
>Radio shack should still have tech manuals for that machine...
> 
> in model 3 mode, video ram starts at 15360 and goes to 16383.  i
>don't know if video ram is normally accessable by applications in model 4
>mode.
>
	More precisly:
	In Model 3 mode: Video is mapped from 0x3C00-0x3FFF
			 Keyboard is mapped 0x3800-0x3BFF
		     The video area is a 64x16 area, one byte is either
		     an ascii character or a graphics character if the 7
		     bit is set and the ALT character set is not enabled.

	In model 4 mode use the system calls to access the keyboard and
	memory, the OS plays bank switching games and you don't want to
	confuse it. Actually, in Model 3 mode you should also go through
	the OS, except for high speed graphics and fast full screen
	updates direct access doesn't really gain you much.

	The Model 4/4p Technical Reference Manual is Cat. #26-2119
	if you can still get one. It has all the hardware dirt on the
	system and also explains all the OS interfaces and system calls.

		-Rob