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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
327
If LFILLI=1 and BLFILL=0, then the TDPR FIFO had fallen below the lower-
threshold state earlier, but has since been refilled to a level above the lower-
threshold level.
Polling 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 0 since packet transmission is set to work with a periodic polling
procedure. The following procedure should be followed to transmit HDLC
packets:
1. Wait until data is available to be transmitted, then go to step 2.
2. Read the TDPR Interrupt Status register.
3. If FULL=1, then the TDPR FIFO is full and no further bytes can be written.
Continue polling the TDPR Interrupt Status register until either FULL=0 or
BLFILL=1. Then, go to either step 4 or 5 depending on implementation
preference.
4. If BLFILL=1, then the TDPR FIFO depth is below its lower threshold limit.
Write the data into the TDPR Transmit Data register. Go to step 6.
5. If FULL=0, then the TDPR FIFO has room for at least 1 more byte to be
written. Write the data into the TDPR Transmit Data register. Go to step 6.
6. If more data bytes are to be transmitted in the packet, then go to step 2.
7. 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.
12.13 Using the Internal Data Link Receiver
It is important to note that the access rate to the RDLC registers is limited by the
rate of the internal high-speed system clock selected by the LINESYSCLK
register bit of the S/UNI-QJET Misc. register (09BH, 19BH, 29BH, 39BH).
Consecutive accesses to the RDLC Status and RDLC Data registers should be
accessed at a rate no faster than 1/10 that of the selected RDLC high-speed
system clock. This time is used by the high-speed system clock to sample the