membus_slow.c

/*! \file membus.c \brief Software-driven Memory Bus for ARMmini-LPC210x. */
//*****************************************************************************
//
// File Name    : 'membus.c'
// Title        : Software-driven Memory Bus for ARMmini-LPC210x
// Author       : Pascal Stang - Copyright (C) 2004
// Created      : 2004.05.05
// Revised      : 2004.07.12
// Version      : 0.1
// Target MCU   : ARM processors
// Editor Tabs  : 4
//
// NOTE: This code is currently below version 1.0, and therefore is considered
// to be lacking in some functionality or documentation, or may not be fully
// tested.  Nonetheless, you can expect most functions to work.
//
// This code is distributed under the GNU Public License
//      which can be found at http://www.gnu.org/licenses/gpl.txt
//
//*****************************************************************************

#include "lpc2000.h"
#include "global.h"
#include "processor.h"
#include "timer.h"
#include "membus.h"

void membusInit(void)
{
    // setup I/O lines
    IOCLR = MEMBUS_LATCH;
    IOSET = MEMBUS_nRD;
    IOSET = MEMBUS_nWR;
    // set inputs
    IODIR &= ~P015;
    // set outputs
    IODIR |= (MEMBUS_IO | MEMBUS_LATCH | MEMBUS_nRD | MEMBUS_nWR);
}

uint16_t membusRead(uint16_t addr)
{
    uint16_t data;
    int flags;

    // disable interrupts
    flags = disableIRQ();
    // switch bus to output
    IODIR |= MEMBUS_IO;
    // assert address
    IOCLR = MEMBUS_IO;
    IOSET = addr<<16;
    // latch address
    IOSET = MEMBUS_LATCH;
    // delay
    MEMBUS_DELAY;
    IOCLR = MEMBUS_LATCH | MEMBUS_IO;
    
    // switch bus to input
    IODIR &= ~MEMBUS_IO;
    // assert read
    IOCLR = MEMBUS_nRD;
    // delay
    MEMBUS_DELAY;
    // read in data
    data = IOPIN>>16;
    // release read
    IOSET = MEMBUS_nRD;
    // restore interrupts
    restoreIRQ(flags);
    
    return data;
}

void membusWrite(uint16_t addr, uint16_t data)
{
    int flags;

    // disable interrupts
    flags = disableIRQ();
    // switch bus to output
    IODIR |= MEMBUS_IO;
    // assert address
    IOCLR = MEMBUS_IO;
    IOSET = addr<<16;
    // latch address
    IOSET = MEMBUS_LATCH;
    // delay
    MEMBUS_DELAY;
    IOCLR = MEMBUS_LATCH | MEMBUS_IO;
    
    // output data
    IOCLR = MEMBUS_IO;
    IOSET = ((uint32_t)data)<<16;
    // assert write
    IOCLR = MEMBUS_nWR;
    // delay
    MEMBUS_DELAY;
    // release write
    IOSET = MEMBUS_nWR;
    // restore interrupts
    restoreIRQ(flags);
}

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