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Path: utzoo!watmath!clyde!cbosgd!neuro1!sob
From: sob@neuro1.UUCP (Stan Barber)
Newsgroups: net.micro.trs-80
Subject: Re: Again: What makes the Model 4 work?
Message-ID: <669@neuro1.UUCP>
Date: Fri, 15-Nov-85 04:03:22 EST
Article-I.D.: neuro1.669
Posted: Fri Nov 15 04:03:22 1985
Date-Received: Sat, 16-Nov-85 09:21:35 EST
References: <408@houem.UUCP>
Reply-To: sob@neuro1.UUCP (Stan Barber)
Organization: Neurophysiology, Baylor College of Medicine, Houston, Tx
Lines: 43


Here is a list of interesting ports for the Model 4.

PORT 84H

Bit 0 and 1 control the enable state of the Model III ROMS and the Video
and keyboard mapping swapout. The following table illustrates this.

BITS   MODEL III ROMS ENABLED		VIDEO/KEYBOARD STATUS
1  0

0  0		YES			  MODEL III MODE
0  1		 NO			  MODEL III MODE
1  0		 NO			  MODEL IV MODE  (IN)
1  1		 NO			  MODEL IV MODE  (OUT)

Bit 2 controls the format of the display.... 0 = 64X16, 1 = 80X24

Bit 3 when on means use reverse video

Bits 4 5 and 6 control RAM bank select accoding to this table.

BITS		Lower 32K RAM		Upper 32K RAM
6 5 4
0 0 0		Bank 0			Bank 1
0 1 0 		Bank 0 			Bank 2
0 1 1		Bank 0			Bank 3
1 1 0		Bank 2			Bank 1
1 1 1		Bank 3			Bank 1

Bit 7 controls what page to map the 64x16 screen into: 0 = page 0, 1=page 1

ports 88-8BH are ports on the CRT controller, but I don't know how they work.
I can tell you that the CRT controller is a 68054. If you get more info here,
please forward it.

90H allows you to sound the sound board.

Hope this helps. Sorry to not be so helpful the last time.
-- 
Stan		uucp:{ihnp4!shell,rice}!neuro1!sob     Opinions expressed
Olan		ARPA:sob@rice.arpa		       here are ONLY mine &
Barber		CIS:71565,623   BBS:(713)660-9262      noone else's.