Path: utzoo!mnetor!uunet!husc6!bloom-beacon!mit-eddie!uw-beaver!cornell!batcomputer!braner
From: braner@batcomputer.tn.cornell.edu (braner)
Newsgroups: comp.sys.atari.st
Subject: Re: st keyboard buffering
Message-ID: <4694@batcomputer.tn.cornell.edu>
Date: 5 May 88 13:19:33 GMT
References: <4215@dasys1.UUCP> <478@philmds.UUCP>
Reply-To: braner@tcgould.tn.cornell.edu (braner)
Organization: Cornell Theory Center, Cornell University, Ithaca NY
Lines: 47
Keywords: keyboard input Crawcin Bconin
Summary: some comments

[]

In article <478@philmds.UUCP> leo@philmds.UUCP (L.J.M. de Wit) writes:

>Here's how keyboard buffering is done (at least I thought so ...) :
>The keyboard ACIA chip reads the keyboard and makes the characters available
>... The processor, as part of the VBL routine, reads the byte...

- the keyboard (and mouse and joystick) events have their own interrupt.

>#define CONTROLC 0x2e0003
> ...
>    for (i = iop->ibufhead; i != iop->ibuftail; ) { 

- note that what "they" call head and tail may be the reverse of what you
 (or I, anyway) would call them...

>        if (*(int *)(iop->ibuf + i) == CONTROLC) {

- this may fail if "conterm" is set so that the kbdshift info is in the top
 byte of the top word.  Better use:
	if (((*(int *)(iop->ibuf + i)) & 0xFF00FF) == CONTROLC)
	                               ^^^^^^^^^^
>    a) Lattice has int == 4 bytes, short == 2 (Megamax I thought int == 2).
>       So you should replace the *(int *) by *(long *), and the short by int.

- yup, in Megamax (and Laser) int==16 bits, long==32 bits.  Avoid shorts.
  (I _think_ they're 8 bits in old Megamax, 16 in Laser.)
  Better to write code like this:

	#define WORD int	/* this is for megamax */
	...
	... WORD ...		/* all through the code where it matters */

  (Makes it a lot easier to port to another compiler.)

>I hope this helps and is raw enough? Have a nice byte ( %-) !

- thanks, Leo!

>           Leo. (What you C is what you get).

- Moshe Braner.  (YAFIYGI) (You asked for it, you got it.) (TeX)

(Still looking for a used 520ST system)

STOP CONTRA AID:  BOYCOTT COCAINE