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PM7346 S/UNI-QJET
DATASHEET
PMC-960835
ISSUE 6
SATURN QUAD USER NETWORK INTERFACE FOR J2, E3, T3
PMC-SIERRA, INC. PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA INC., AND ITS CUSTOMERS’ INTERNAL USE
325
Interrupt Identification register, and the S/UNI-QJET Interrupt Status register to
identify TDPR interrupts which determine when writes can or must be done to
the TDPR Transmit Data register.
Interrupt Driven Mode
The TDPR automatically transmits a packet once it is completely written into the
TDPR FIFO. The TDPR also begins transmission of bytes once the FIFO level
exceeds the programmable Upper Transmit Threshold. The CRC bit can be set to
logic 1 so that the FCS is generated and inserted at the end of a packet. The
TDPR Lower Interrupt Threshold should be set to such a value that sufficient
warning of an underrun is given. The FULLE, LFILLE, OVRE, and UDRE bits are
all set to logic 1 so an interrupt on INTB is generated upon detection of a FIFO
full state, a FIFO depth below the lower limit threshold, a FIFO overrun, or a
FIFO underrun. The following procedure should be followed to transmit HDLC
packets:
1. Wait for data to be transmitted. Once data is available to be transmitted, then
go to step 2.
2. Write the data byte to the TDPR Transmit Data register.
3. If all bytes in the packet have been sent, then set the EOM bit in the TDPR
Configuration register to logic 1. Go to step 1.
4. If there are more bytes in the packet to be sent, then go to step 2.
While performing steps 1 to 4, the processor should monitor for interrupts
generated by the TDPR. When an interrupt is detected, the TDPR Interrupt
Routine detailed in the following text should be followed immediately.
The TDPR will force transmission of the packet information when the FIFO depth
exceeds the threshold programmed with the UTHR[6:0] bits in the TDPR Upper
Transmit Threshold register. Unless an error condition occurs, transmission will
not stop until the last byte of all complete packets is transmitted and the FIFO
depth is at or below the threshold limit. The user should watch the FULLI and
LFILLI interrupts to prevent overruns and underruns.
TDPR Interrupt Routine
Upon assertion of INTB, the source of the interrupt must first be identified by
reading the S/UNI-QJET Clock Activity Monitor and Interrupt Identification
register (007H) and the S/UNI-QJET Interrupt Status registers (005H, 105H,