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Communication Processor Module
16-362
MPC823 USER’S MANUAL
MOTOROLA
USB
COMMUNICATION
16
PROCESSOR
MODULE
I—Interrupt
0 = No interrupt is generated after this buffer has been serviced.
1 = The TXB or the appropriate TXEx bit in the USBER is set when this buffer is
serviced. TXB and TXEx can cause interrupts if they are enabled.
L—Last
0 = This buffer does not contain the last character of the message.
1 = This buffer contains the last character of the message.
TC—Transmit CRC
This bit is only valid when the L bit is set. Otherwise, it is ignored.
0 = Transmit end-of-packet after the last data byte. This setting can be used for testing
purposes to send a bad CRC after the data.
1 = Transmit the CRC sequence after the last data byte.
CNF—Transmit Confirmation
This bit is only valid when the L bit is set. Otherwise, it is ignored.
0 = Continue to load the transmitter FIFO with the next packet. No handshake or
response is expected from the function for this packet.
1 = Wait for handshake or response from the function before stating the next packet or
this is the last packet.
PID—Packet ID
This field is set by the USB controller to indicate the type of the packet. It is only valid if the
F bit is set. This field is written by the USB controller after the received data has been placed
into the associated data buffer.
NAK—NAK Handshake Received
This bit indicates that the endpoint has responded with a NAK handshake. The packet was
received error-free, however, the endpoint could not accept it. This bit is written by the USB
controller after it has finished transmitting the associated data buffer.
STAL—STALL Handshake Received
This bit indicates that the endpoint has responded with a STALL handshake. The endpoint
needs attention through the control pipe. This bit is written by the USB controller after it has
finished transmitting the associated data buffer.
TO—Time-Out
This bit indicates that the endpoint has failed to acknowledge this packet. This bit is written
by the USB controller after it has finished transmitting the associated data buffer.
Note: You cannot set CNF = 0 for a token that should be followed by a data packet if
the data packet buffer descriptor is not ready.