A85: Port 4

To: assembly-85@lists.ticalc.org
Subject: A85: Port 4
From: Sam Heald <evil_sam@hotmail.com>
Date: Fri, 25 Jun 1999 10:47:51 PDT
Delivered-To: assembly-85-outgoing@towerguard.unix.edu.sollentuna.se
Delivered-To: assembly-85@lists.ticalc.org
Reply-To: assembly-85@lists.ticalc.org


  Can anyone on this list explain how to use port 4? I could only find the 
information below. According to it, if I wrote:

ld a,%00001110
out (4),a

   then the LCD width would 12 bytes, the same as an 82. This would be very 
useful to porting 82 games, but for some reason it doesn't work.


>From TI-PORTS.TXT:

----------------------------------------------------------------------
Port 4 : Video Buffer Width, Interrupt Control                   Write Only
----------------------------------------------------------------------
Write
-----
XXX....?
Bits 4 and 3 = Video Buffer Width
               00: 10-byte wide buffer
               01: 12-byte wide buffer
               10: 16-byte wide buffer (normal)
               11: 20-byte wide buffer
Bits 2 and 1 = Interrupt speed (11 = normal 00=fastest)
               00: black screen and frozen calculator
               01: dark screen, top half of screen is doubled in lower half,
                   and interrupts go faster
               10: slightly darker than normal screen, top 1/4 of screen is
                   doubled in bottom 1/4, slightly faster interrupts
               11: normal
Bit 0 = 1: freeze       \_ don't know what this does
        0: function     /

--------


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