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DACS: Pbus Driver Code, pbus.c

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Pbus Driver Code, `pbus.c`

The code that implements the Pbus driver is presented below.

/*****************************************************************************
 * DACS : Distributed Audio Control System
 *============================================================================
 *         File: pbus.c
 *       Author: Stephen S. Richardson
 * Date Created: 04.14.97
 *  Environment: ICC11 v4.0, 68HC11 target
 *        Build: library, not standalone
 *============================================================================
 * The code, executables, documentation, firmware images, and all related
 * material of DACS are  
 * Copyright (C) 1997 Stephen S. Richardson - ALL RIGHTS RESERVED
 *****************************************************************************
 * Source code control:
 *
 * $Id: pbus.c,v 1.1 1997/07/23 21:30:10 prefect Exp prefect $
 *
 *****************************************************************************/

#include <hc11.h>
#include "pbus.h"
#include "pbusdefn.h"


/*****************************************************************************
 * pbus_init
 *
 * initializes pBUS controller, appropriate bits, etc.
 *****************************************************************************/
void pbus_init (void)
{
  PBC_PX=PBC_OX;                         /* pBUS in output mode */
  PBC_PA=0;                              /* pBUS data bus = 0 */
  PBC_PB=0;                              /* pBUS addx bus = 0 */
  PBC_PC|=PB_N_LATCH|PB_N_CLOCK;         /* pBUS latch- and clock- inactive */

}

/*****************************************************************************
 * pbus_lwrite
 *
 * does a standard pBUS latch write operation; writes data to pBUS addx.
 *****************************************************************************/
void pbus_lwrite (unsigned char addx, unsigned char data)
{
  PBC_PX=PBC_OX;                         /* pBUS in output mode */
  PBC_PC|=PB_N_LATCH|PB_N_CLOCK;         /* pBUS latch- and clock- inactive */

  PBC_PA=data;                           /* data on pBUS */
  PBC_PB=addx|PB_N_RD_WR;                /* addx on pBUS, write mode */
  PBC_PC&=~PB_N_LATCH;                   /* pBUS latch- active */
  PBC_PC|=PB_N_LATCH;                    /* pBUS latch- inactive */
}


/*****************************************************************************
 * pbus_lread
 *
 * does a standard pBUS latch read operation; returns pBUS data from addx
 *****************************************************************************/
unsigned char pbus_lread (unsigned char addx)
{
  unsigned char c;

  PBC_PX=PBC_IX;                         /* pBUS in input mode */
  PBC_PC|=PB_N_LATCH|PB_N_CLOCK;         /* pBUS latch- and clock- inactive */

  PBC_PB=addx&~PB_N_RD_WR;               /* addx on pBUS, read mode */
  PBC_PC&=~PB_N_LATCH;                   /* pBUS latch- active */
  c=PBC_PA;                              /* data from pBUS */
  PBC_PC|=PB_N_LATCH;                    /* pBUS latch- inactive */
  return (c);
}

Steve Richardson 2000-07-06

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