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From: nparker@cie-2.uoregon.edu (Neil Parker)
Newsgroups: comp.sys.apple2
Subject: Re: Clock, BASIC, and IIgs
Date: 12 Jun 1996 07:52:02 GMT
Organization: University of Oregon Campus Information Exchange
Lines: 86
Message-ID: <4plsv2$rml@pith.uoregon.edu>
References: <4plje3$2td@news.nevada.edu>
NNTP-Posting-Host: cie-2.uoregon.edu

In article <4plje3$2td@news.nevada.edu> snit@nevada.edu (Snit) writes:
>Does anybody know how to access the clock from BASIC on a IIgs?  Is
>there a way of doing something similaron a IIe (obviosly not wth the
>real time, unless you have a clock added).  Specificly, I am trying to
>record the times of a photosensor attached to PDL (0) into a text file
>that can be imported into a spreadsheet or stats program.  Thanks...

There are no BASIC commands for accessing the clock--the only good way to
do it is to call a machine-language routine.

The most portable way to access the clock is through ProDOS.  Your BASIC
program calls this machine-language routine:

     JSR $BF00
     DFB $82     ; GET_TIME
     DW  0
     RTS

Then you can PEEK the time and date out of the ProDOS global page.  The
minute is PEEK(49042), and the hour is PEEK(49043).  The date is in
PEEK(49040) and PEEK(49041), but after PEEKing it, you have to unpack it
before you can use it (see the example below).

     10  FOR X = 0 TO 6: READ Y: POKE 768 + X,Y: NEXT
     20  DATA 32,0,191,130,0,0,96: REM Machine code
     30  CALL 768
     40 HR =  PEEK (49043): REM Hour (0..23)
     50 MI =  PEEK (49042): REM Minute (0..59)
     60 D =  PEEK (49040) + 256 *  PEEK (49041)
     70 X =  INT (D / 32)
     80 DA =  D - 32 * X: REM Day (1..31)
     90 D = X:X = INT (D / 16)
     100 MO =  D - 16 * X: REM Month (1..12)
     110 YR = X + 1940: REM Year (1940..2039)

If the day and the month are both zero, then either no clock is available,
or ProDOS doesn't have a driver for the clock.

The drawback of this method, of course, is that you only get one-minute
resolution.  If you want to time events more accurately than that, you'll
have to use more complicated methods.


The GS clock can provide one-second resolution.  The easiest (and only
Officially Suppored) way to get it is to call the Miscellaneous Toolset.
Again, you need to CALL a machine-language routine:

     clc          ; switch to native mode
     xce
     rep #$30
     pha          ; push space for result
     pha
     pha
     pha
     ldx #$0D03   ; ReadTimeHex
     jsl $E10000
     sec          ; back to emulation mode
     xce
     ldx #7       ; pop results and save
l1   pla
     sta $200,X
     dex
     bpl l1
     rts

This routine leave the clock values in the following memory locations:

     PEEK(512) -- weekday (1..7, 1=Sunday)
     PEEK(513) -- (not used)
     PEEK(514) -- month (0..11)
     PEEK(515) -- day (0..30)
     PEEK(516) -- year minus 1900
     PEEK(517) -- hour (0..23)
     PEEK(518) -- minute (0..59)
     PEEK(519) -- second (0..59)

(Sorry...no BASIC example this time.  I'm not feeling quite ambitious
enough to hand-assemble that machine language and convert it to DATA
statements.)

            - Neil Parker
-- 
Neil Parker, nparker@{cie-2,cie}.uoregon.edu, http://cie-2.uoregon.edu/~nparker

     "Evolution is vastly overrated."  -- Ambassador Delenn, _Babylon_5_