AN2120: Connecting an M68HC08 Family Microcontroller to an ...

#include "CommDrv.h"
#include "ModemDrv.h"
#define MODEM_BUFFER_SIZE 32 // Size of Modem Buffer
AN2120
Application Note
Code Implementation
#define DTR_ON PORTD &= 0xFE; // DTR Pin is PORTD0, Macro to set it ON
#define DTR_OFF PORTD |= 0x01; // Macro to set DTR OFF
#define DTR_PIN (PORTD & 0x01) // DTR Pin = Pin 0 of PORT D
// Byte pointers of the ring buffer (FIFO)
volatile BYTE mDataSlot = 0; // Points to the next available character
volatile BYTE mEmptySlot = 0; // Points to next available slot of the FIFO
static BYTE *ModemBuffer; // Pointer to Modem buffer
/***********************************************************************
Function : ModemInit
Parameters : None
Date : December 2000
Desc : Initializes the ring buffer & clears the DTR pin
***********************************************************************/
void ModemInit (void) {
mDataSlot = 0; // Initialize FIFO Modem pointers
mEmptySlot = 0;
DDRD |= 0x01; // DTR pin set to output
DTR_OFF; // DTR Off
}
/***********************************************************************
Function : ModemBuffFlush
Parameters : None
Date : January 2001
Desc : Flushes the receiving FIFO (ring buffer)
***********************************************************************/
void ModemBuffFlush (void) {
mDataSlot = mEmptySlot;
}
/***********************************************************************
Function : ModemDial
Parameters : A string containing the phone number to dial
Date : December 2000
MOTOROLA 73