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From: gwyn@BRL.ARPA (Doug Gwyn, VLD/VMB)
Newsgroups: comp.sys.apple
Subject: IIGS SCC info
Message-ID: <8705210443.aa02621@SMOKE.BRL.ARPA>
Date: Thu, 21-May-87 04:43:46 EDT
Article-I.D.: SMOKE.8705210443.aa02621
Posted: Thu May 21 04:43:46 1987
Date-Received: Sat, 23-May-87 12:35:02 EDT
Sender: daemon@ucbvax.BERKELEY.EDU
Distribution: world
Organization: The ARPA Internet
Lines: 51

In an accompanying message is a C header file I use on my Apple IIGS
to define macros for using the Zilog 8530L Serial Communications
Controller that controls access to the "printer" and "modem" ports.
That file is heavily commented and gives references for further details.
The following is a portion of the C source for a program that uses the
header file in order to directly control the printer port, as an example
of usage of the macros.

/*
	example of "scc8530.h" usage -- taken from a printout utility
*/

#include	"scc8530.h"

static void
prinit()
	{
	char	warned = 0;

	SCCA_ctrl( 9, WR9_RSTA );
	SCCA_ctrl( 10, WR10_NRZ | WR10_MIDLE );
	SCCA_ctrl( 11, WR11_RXTAL | WR11_RBRG | WR11_TBRG );
	SCCA_ctrl( 12, X16_9600 );
	SCCA_ctrl( 13, X16_9600 >> 8 );
	SCCA_ctrl( 15, 0 );
	SCCA_ctrl( 0, WR0_RUND | WR0_RERR );
	SCCA_ctrl( 1, WR1_RIDIS );
	SCCA_ctrl( 4, WR4_X16 | WR4_1SB );
	SCCA_ctrl( 14, WR14_DPLL | WR14_BREN );
	SCCA_ctrl( 3, WR3_R8B | WR3_SCLI | WR3_RXEN );
	SCCA_ctrl( 5, WR5_T8B | WR5_TXEN | WR5_RTS );

	while ( (SCCA_stat( 0 ) & RR0_CTS) == 0 )
		if ( warned == 0 )
			{
			write( 2, "\007printer off-line\n", 18 );
			++warned;
			}
	}

static void
prc( c )
	int	c;
	{
	while ( (SCCA_stat( 0 ) & (RR0_CTS | RR0_EMPTY)) !=
		(RR0_CTS | RR0_EMPTY)
	      )
		;			/* wait until transmitter ready */

	SCCA_out( c );
	}