PM7344 S/UNI-MPH
DATA SHEET
PMC-950449
ISSUE 6
MULTI-PHY USER NETWORK INTERFACE
2) An abort sequence is detected while not in the receiving all-ones state
and the byte, written to the FIFO due to the detection of the abort sequence,
is being read from the FIFO,
3) The first flag has been detected and the dummy byte, written into the
FIFO when the RFDL changes from the receiving all-ones state to the
receiving flags state, is being read from the FIFO,
4) Immediately on detection of FIFO overrun.
The EOM bit is passed through the FIFO with the Data so that the Status will
correspond to the Data just read from the FIFO.
FLG:
The flag bit (FLG) is set if the RFDL has detected the presence of the HDLC
flag sequence (01111110) in the data. FLG is reset only when the HDLC
abort sequence (01111111) is detected in the data or when the RFDL is
disabled. This bit is passed through the FIFO with the Data so that the Status
will correspond to the Data just read from the FIFO. The reception of bit-
oriented codes over the data link will also force an abort due to its eight ones
pattern.
OVR:
The Receiver Overrun bit (OVR) is set when data is written over unread data
in the FIFO. This bit is not reset until after the Status register is read. While
OVR is high, the RFDL and FIFO are held in the reset state, causing the FLG
and EOM bits in the status register to be reset also.
FE:
The FIFO Empty bit (FE) is high when the last FIFO entry is read and goes
low when the FIFO is loaded with new data.
If the RFDL Receive Data register is read while there is no valid data, then a
FIFO underrun condition occurs. The underrun condition is reflected in the Status
register by forcing all bits to logic zero on the first Status register read
immediately following the Received Data register read which caused the
underrun condition.
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
139
PMC [ PMC-SIERRA, INC ]
