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From: rubywand@aol.com (RUBYWAND)
Newsgroups: comp.sys.apple2.programmer
Subject: Re: HELP - IIgs timer...
Date: 16 Mar 1996 07:38:34 -0500
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In article <4i7mgg$sse@leonard.anu.edu.au>,
Kristen Maria Pammer wrote:

>The program basically sets up the timer using a few "POKE" commands
>then sits in a loop waiting for a specific value to appear in a certain
>location, which it polls using "PEEK".  The problem is that the program 
>just seems to hang indefinitely in this loop - the value it is waiting 
>for never shows up. 
>
> What I want to know, is: is it possible that the 
>timer is mapped to a different memory location on my IIgs to the one that

>the program originally ran on? is there any other likely cause to this 
>problem?

    You are not likely to find a hardware timer on the IIgs with the same
output address(es) as one employed on a II+ or IIe.

    A fix is to use a Toolbox CALL which reads the IIgs clock and places
the result in a memory location you specify. You can poke the code into
the $0300 area (or BLOAD it). The BASIC routine could look something like

 50 CALL 768: REM CALL routine which does CALL to ReadTimeHex
 60 TC = PEEK(815): REM assumes routine puts Seconds at $32F
 70 IF TC <> TE THEN GOTO 50: REM TE is the end/exit value you set
 80 RETURN

    The subroutine is good for waits of up to 60 seconds. It should cycle
fast enough to guarantee that the TC = TE condition will not be missed.

    For longer waits, line 60 might be

 60 TC = 60 * PEEK(816) +  PEEK(815): REM 60 x Minutes + Seconds

    This kind of thing starts to take time at "normal" speed. To make sure
you do not miss TC = TE you will probably want the routine to avoid
unnecessary delays:

 50 CALL 768: IF 60 * PEEK(816) +  PEEK(815) <> TE THEN 50
 80 RETURN


    Machine code for a routine which CALLs ReadTimeHex and saves Seconds
and Minutes at $32F, $330 is shown below:
 
300: 18                 First, set Native mode with 16 bit registers
301: FB
302: C2 30 
304: 48                 Push 4 words of 'workspace' onto stack
305: 48
306: 48
307: 48
308: A2 03 0D       Put ReadTimeHex tool ID in X
30B: 22 00 00 E1  JSR long to dispatcher to do the Read
30F: 68                 Pull MinSec result word from Stack (Lo byte =
Seconds)
310: 8D 2F 03       Save result word at $32F
313: 68                 (YrHour) Pull other three result words to restore
stack
314: 68                 (MoDay)
315: 68                 (WkdayNull)
316: E2 30            Restore Emulation mode with 8-bit registers
318: 38
319: FB
31A: 60                Exit back to BASIC
 

Rubywand