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DS3171/DS3172/DS3173/DS3174
164
Register Name:
HDLC.RFDR
Register Description:
HDLC Receive FIFO Data Register
Register Address:
(0,2,4,6)BCh
Bit
# 15 14 13 12 11 10 9 8
Name RFD7 RFD6 RFD5 RFD4 RFD3 RFD2 RFD1 RFD0
Default
X X X X X X X X
Bit
# 7 6 5 4 3 2 1 0
Name
-- -- -- --
RPS2 RPS1 RPS0 RFDV
Default
0 0 0 0 X X X 0
Note: The FIFO data and status are updated when the Receive FIFO Data (RFD[7:0]) is read (upper byte read).
When this register is read eight bits at a time, a read of the lower byte will reflect the status of the next read of the
upper byte, and reading the upper byte when RFDV=0 may result in a loss of data.
Bits 15 to 8: Receive FIFO Data (RFD[7:0])
– These eight bits are the packet data stored in the Receive FIFO.
RFD[7] is the MSB, and RFD[0] is the LSB. If bit reordering is disabled, RFD[0] is the first bit received, and RFD[7]
is the last bit received. If bit reordering is enabled, RFD[7] is the first bit received, and RFD[0] is the last bit
received.
Bits 3 to 1: Receive Packet Status (RPS[2:0])
– These three bits indicate the status of the received packet and
packet data.
000 = packet middle
001 = packet start.
010 = reserved
011 = reserved
100 = packet end: good packet
101 = packet end: FCS errored packet.
110 = packet end: invalid packet (a non-integer number of bytes).
111 = packet end: aborted packet.
Bit 0: Receive FIFO Data Valid (RFDV)
– When 0, the Receive FIFO data (RFD[7:0]) is invalid (the Receive FIFO
is empty). When 1, the Receive FIFO data (RFD[7:0]) is valid.