
STANDARD PRODUCT
PM8315 TEMUX
DATASHEET
PMC-1981125
ISSUE 7
HIGH DENSITY T1/E1 FRAMER  WITH
INTEGRATED VT/TU MAPPER AND M13 MUX
PROPRIETARY AND CONFIDENTIAL
195
5. If LFILLI=1 and BLFILL=1, then the TDPR FIFO depth is below its lower
threshold limit.  If there is more data to transmit, then it should be written to
the TDPR Transmit Data register before an underrun occurs.  If there is no
more data to transmit, then an EOM should be set at the end of the last
packet byte.  Flags will then be transmitted once the last packet has been
transmitted.
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.
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.