/**
*
* This function handles data received from the IIC bus as a slave.
*
* When the slave expects more than the master has to send, the slave will stall
* waiting for data.
*
* When more data is received than data expected a Nack is done to signal master
* to stop sending data. The excess data is discarded to prevent bus throttling.
*
* The buffer may be full and the master continues to send data if the master
* and slave have different message lengths. This condition is handled by sending
* No Ack to the master and reading Rx data until the master stops sending data
* to prevent but throttling from locking up the bus. To ever receive as a slave
* again, must know when to renable bus ACKs. NAAS is used to detect when the
* master is finished sending messages for any mode.
* @param InstancePtr is a pointer to the XIic instance to be worked on.
*
* @return None.
*
* @note None.
*
******************************************************************************/
static void RecvSlaveData(XIic *InstancePtr)
{
u32 CntlReg;
u8 BytesToRead;
u8 LoopCnt;
u8 Temp;
/*
* When receive buffer has no room for the receive data discard it.
*/
if (InstancePtr->RecvByteCount == 0) {
/*
* Set ACKnowlege OFF to signal master to stop sending data.
*/
CntlReg = XIic_ReadReg(InstancePtr->BaseAddress,
XIIC_CR_REG_OFFSET);
CntlReg |= XIIC_CR_NO_ACK_MASK;
XIic_WriteReg(InstancePtr->BaseAddress, XIIC_CR_REG_OFFSET,
CntlReg);
/*
* Clear excess received data to prevent bus throttling and set
* receive FIFO occupancy to throttle at the 1st byte received.
*/
XIic_FlushRxFifo(InstancePtr);
XIic_WriteReg(InstancePtr->BaseAddress,
XIIC_RFD_REG_OFFSET, 0);
return;
}
/*
* Use occupancy count to determine how many bytes to read from the
* FIFO, count is zero based so add 1, read that number of bytes from
* the FIFO.
*/
BytesToRead = (XIic_ReadReg(InstancePtr->BaseAddress,
XIIC_RFO_REG_OFFSET)) + 1;
for (LoopCnt = 0; LoopCnt < BytesToRead; LoopCnt++) {
XIic_ReadRecvByte(InstancePtr);
}
/*
* Set receive FIFO depth for the number of bytes to be received such
* that a receive interrupt will occur, the count is 0 based, the
* last byte of the message has to be received seperately to ack the
* message.
*/
if (InstancePtr->RecvByteCount > IIC_RX_FIFO_DEPTH) {
Temp = IIC_RX_FIFO_DEPTH - 1;
} else {
if (InstancePtr->RecvByteCount == 0) {
Temp = 0;
} else {
Temp = InstancePtr->RecvByteCount - 1;
}
}
XIic_WriteReg(InstancePtr->BaseAddress,
XIIC_RFD_REG_OFFSET, (u32) Temp);
return;
}
/**
*
* This function is called when the receive register is full. The number
* of bytes received to cause the interrupt is adjustable using the Receive FIFO
* Depth register. The number of bytes in the register is read in the Receive
* FIFO occupancy register. Both these registers are zero based values (0-15)
* such that a value of zero indicates 1 byte.
*
* For a Master Receiver to properly signal the end of a message, the data must
* be read in up to the message length - 1, where control register bits will be
* set for bus controls to occur on reading of the last byte.
*
* @param InstancePtr is a pointer to the XIic instance to be worked on.
*
* @return None.
*
* @note None.
*
******************************************************************************/
static void RecvMasterData(XIic *InstancePtr)
{
u8 LoopCnt;
int BytesInFifo;
int BytesToRead;
u32 CntlReg;
/*
* Device is a master receiving, get the contents of the control
* register and determine the number of bytes in fifo to be read out.
*/
CntlReg = XIic_ReadReg(InstancePtr->BaseAddress, XIIC_CR_REG_OFFSET);
BytesInFifo = XIic_ReadReg(InstancePtr->BaseAddress,
XIIC_RFO_REG_OFFSET) + 1;
/*
* If data in FIFO holds all data to be retrieved - 1, set NOACK and
* disable the Tx error.
*/
if ((InstancePtr->RecvByteCount - BytesInFifo) == 1) {
/*
* Disable Tx error interrupt to prevent interrupt
* as this device will cause it when it set NO ACK next.
*/
XIic_DisableIntr(InstancePtr->BaseAddress,
XIIC_INTR_TX_ERROR_MASK);
XIic_ClearIntr(InstancePtr->BaseAddress,
XIIC_INTR_TX_ERROR_MASK);
/*
* Write control reg with NO ACK allowing last byte to
* have the No ack set to indicate to slave last byte read.
*/
XIic_WriteReg(InstancePtr->BaseAddress, XIIC_CR_REG_OFFSET,
(CntlReg | XIIC_CR_NO_ACK_MASK));
/*
* Read one byte to clear a place for the last byte to be read
* which will set the NO ACK.
*/
XIic_ReadRecvByte(InstancePtr);
}
/*
* If data in FIFO is all the data to be received then get the data
* and also leave the device in a good state for the next transaction.
*/
else if ((InstancePtr->RecvByteCount - BytesInFifo) == 0) {
/*
* If repeated start option is off then the master should stop
* using the bus, otherwise hold the bus, setting repeated start
* stops the slave from transmitting data when the FIFO is read.
*/
if ((InstancePtr->Options & XII_REPEATED_START_OPTION) == 0) {
CntlReg &= ~XIIC_CR_MSMS_MASK;
} else {
CntlReg |= XIIC_CR_REPEATED_START_MASK;
}
XIic_WriteReg(InstancePtr->BaseAddress, XIIC_CR_REG_OFFSET,
CntlReg);
/*
* Read data from the FIFO then set zero based FIFO read depth
* for a byte.
*/
for (LoopCnt = 0; LoopCnt < BytesInFifo; LoopCnt++) {
XIic_ReadRecvByte(InstancePtr);
}
XIic_WriteReg(InstancePtr->BaseAddress,
XIIC_RFD_REG_OFFSET, 0);
/*
* Disable Rx full interrupt and write the control reg with ACK
* allowing next byte sent to be acknowledged automatically.
*/
XIic_DisableIntr(InstancePtr->BaseAddress,
XIIC_INTR_RX_FULL_MASK);
XIic_WriteReg(InstancePtr->BaseAddress, XIIC_CR_REG_OFFSET,
(CntlReg & ~XIIC_CR_NO_ACK_MASK));
/*
* Send notification of msg Rx complete in RecvHandler callback.
*/
InstancePtr->RecvHandler(InstancePtr->RecvCallBackRef, 0);
} else {
/*
* Fifo data not at n-1, read all but the last byte of data
* from the slave, if more than a FIFO full yet to receive
* read a FIFO full.
*/
BytesToRead = InstancePtr->RecvByteCount - BytesInFifo - 1;
if (BytesToRead > IIC_RX_FIFO_DEPTH) {
BytesToRead = IIC_RX_FIFO_DEPTH;
}
/*
* Read in data from the FIFO.
*/
for (LoopCnt = 0; LoopCnt < BytesToRead; LoopCnt++) {
XIic_ReadRecvByte(InstancePtr);
}
}
}
/**
*
* This function is called when the IIC device receives Not Addressed As Slave
* (NAAS) interrupt which indicates that the master has released the bus implying
* a data transfer is complete.
*
* @param InstancePtr is a pointer to the XIic instance to be worked on.
*
* @return None.
*
* @note None.
*
******************************************************************************/
static void NotAddrAsSlaveHandler(XIic *InstancePtr)
{
u32 Status;
u32 CntlReg;
u8 BytesToRead;
u8 LoopCnt;
/*
* Disable NAAS so that the condition will not continue to interrupt
* and enable the addressed as slave interrupt to know when a master
* selects a slave on the bus.
*/
XIic_DisableIntr(InstancePtr->BaseAddress, XIIC_INTR_NAAS_MASK);
XIic_ClearEnableIntr(InstancePtr->BaseAddress, XIIC_INTR_AAS_MASK);
/*
* Flush Tx FIFO by toggling TxFIFOResetBit. FIFO runs normally at 0
* Do this incase needed to Tx FIFO with more than expected if what
* was set to Tx was less than what the Master expected - read more
* from this slave so FIFO had junk in it.
*/
XIic_FlushTxFifo(InstancePtr);
/*
* NAAS interrupt was asserted but received data in recieve FIFO is
* less than Rc_FIFO_PIRQ to assert an receive full interrupt,in this
* condition as data recieved is valid we have to read data before FIFO
* flush.
*/
Status = XIic_ReadReg(InstancePtr->BaseAddress, XIIC_SR_REG_OFFSET);
if (!(Status & XIIC_SR_RX_FIFO_EMPTY_MASK))
{
BytesToRead = (XIic_ReadReg(InstancePtr->BaseAddress,
XIIC_RFO_REG_OFFSET)) + 1;
if (InstancePtr->RecvByteCount > BytesToRead) {
for (LoopCnt = 0; LoopCnt < BytesToRead; LoopCnt++) {
XIic_ReadRecvByte(InstancePtr);
}
}
}
InstancePtr->RecvByteCount = 0;
/*
* Flush Rx FIFO should slave Rx had a problem, sent No ack but
* still received a few bytes. Should the slave receive have disabled
* acknowledgement, clear Rx FIFO.
*/
XIic_FlushRxFifo(InstancePtr);
/*
* Set FIFO occupancy depth = 1 so that the first byte will throttle
* next recieve msg.
*/
XIic_WriteReg(InstancePtr->BaseAddress, XIIC_RFD_REG_OFFSET, 0);
/*
* Should the slave receive have disabled acknowledgement,
* enable to allow acknowledgment for receipt of our address to
* again be used as a slave.
*/
CntlReg = XIic_ReadReg(InstancePtr->BaseAddress, XIIC_CR_REG_OFFSET);
XIic_WriteReg(InstancePtr->BaseAddress, XIIC_CR_REG_OFFSET,
(CntlReg & ~XIIC_CR_NO_ACK_MASK));
/*
* Which callback depends on messaging direction, the buffer pointer NOT
* being used indicates the direction of data transfer.
*/
Status = XIic_ReadIier(InstancePtr->BaseAddress);
if (InstancePtr->RecvBufferPtr == NULL) {
/*
* Slave was sending data so disable all transmit interrupts and
* call the callback handler to indicate the transfer is
* complete.
*/
XIic_WriteIier(InstancePtr->BaseAddress,
(Status & ~XIIC_TX_INTERRUPTS));
InstancePtr->SendHandler(InstancePtr->SendCallBackRef,
InstancePtr->SendByteCount);
}
else {
/*
* Slave was receiving data so disable receive full interrupt
* and call the callback handler to notify the transfer is
* complete.
*/
XIic_WriteIier(InstancePtr->BaseAddress,
(Status & ~XIIC_INTR_RX_FULL_MASK));
InstancePtr->RecvHandler(InstancePtr->RecvCallBackRef,
InstancePtr->RecvByteCount);
}
return;
}
