Silicon Laboratories SI2494/39, SI2493/57/34/15/04 manual Rev 301

AN93

}

//This is the main ISR handler loop: stay in it until all interrupts are cleared while ( RXFInterrupt TXEInterrupt TimerInterrupt U70Interrupt )

{

//***RXF INTERRUPT***

//Separate RXF interrupt from timer interrupt to reduce the number of HIR1 reads. if ( RXFInterrupt )

{

// MODULUS_MASK is BUFFERSIZE - 1

while ( ( rxBufferSize < MODULUS_MASK ) && ( BytesReceived < 10 ) )

{

readModemByte;

//Set a flag to know that RXF was serviced rxf_processed = 1;

BytesReceived++;

}

//Clear the RXF interrupt if fewer than 3 bytes were read. If more than 3 bytes

//were read from the FIFO the interrupt will be cleared automatically.

if (BytesReceived < 3)

{

ClearRXF;	//	Clear RXF since we didn't empty the FIFO
control_update = 1;

}

}

//***TIMER INTERRUPT***

//If there wasn't an RXF interrupt, but the receive FIFO isn't empty,

//the interrupt may have been caused by the receive timer interrupt.

//Note: If the host cannot empty its queue fast enough to keep up with the

//modem or if it is going to have a long period of time (>:U6F setting) where

//there won't be room in the FIFO, it would be better to completely disable

//the interrupt until the host has made room for more data. The timer interrupt

//can only be cleared by reading a byte from the FIFO; if there is no room

//in the FIFO, the interrupt will not be cleared. Alternatively, the routine

//could read a byte to clear the interrupt and then discard the data.

//MODULUS_MASK is BUFFERSIZE - 1

while ( TimerInterrupt && ( rxBufferSize < MODULUS_MASK ) )

{

//Read a byte readModemByte; BytesReceived++;

//Check the status to see if the FIFO is empty ReadModemStatus;

}

//***U70 INTERRUPT***

//Check for a "software" interrupt. "software" refers to any of the interrupts

//described in U70 in the modem datasheet. Only do this if the

//software interrupt is not masked. This is the reason for the bit shift.

if ( U70Interrupt )

{

//Mask the interrupt so that it doesn't cause another interrupt

//until the host software clears it with AT:I and tells us to

//turn it back on

ClearINTM;

control_update = 1;

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