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DS3171/DS3172/DS3173/DS3174
161
12.6.2 HDLC Receive Side Register Map
The receive side utilizes five registers.
Table 12-18. Receive Side HDLC Register Map
Address
Register
Register Description
(0,2,4,6)B0h HDLC.RCR
HDLC Receive Control Register
(0,2,4,6)B2h -- Unused
(0,2,4,6)B4h HDLC.RSR
HDLC Receive Status Register
(0,2,4,6)B6h HDLC.RSRL
HDLC Receive Status Register Latched
(0,2,4,6)B8h HDLC.RSRIE
HDLC Receive Status Register Interrupt Enable
(0,2,4,6)BAh -- Unused
(0,2,4,6)BCh HDLC.RFDR
HDLC Receive FIFO Data Register
(0,2,4,6)BEh -- Unused
12.6.2.1 Register Bit Descriptions
Register Name:
HDLC.RCR
Register Description:
HDLC Receive Control Register
Register Address:
(0,2,4,6)B0h
Bit
# 15 14 13 12 11 10 9 8
Name
--
--
--
RDAL4 RDAL3 RDAL2 RDAL1 RDAL0
Default
0 0 0 0 1 0 0 0
Bit
# 7 6 5 4 3 2 1 0
Name
-- -- -- --
RBRE
RDIE
RFPD
RFRST
Default
0 0 0 0 0 0 0 0
Bits 13 to 8: Receive HDLC Data Available Level (RDAL[4:0])
– These five bits indicate the minimum number of
eight byte groups that must be stored (contain data) in the Receive FIFO before HDLC data is considered to be
available (RHDA=1). For example, a value of 21 (15h) results in HDLC data being available when the Receive
FIFO contains 168 (A8h) bytes or more.
Bit 3: Receive Bit Reordering Enable (RBRE)
– When 0, bit reordering is disabled (The first bit received is in the
LSB of the Receive FIFO Data byte RFD[0]). When 1, bit reordering is enabled (The first bit received is in the MSB
of the Receive FIFO Data byte RFD[7]).
Bit 2: Receive Data Inversion Enable (RDIE)
– When 0, the incoming data is directly passed on for packet
processing. When 1, the incoming data is inverted before being passed on for packet processing.
Bit 1: Receive FCS Processing Disable (RFPD)
– When 0, FCS processing is performed (the packets have an
FCS appended). When 1, FCS processing is disabled (the packets do not have an FCS appended).
Bit 0: Receive FIFO Reset (RFRST)
– When 0, the Receive FIFO will resume normal operations, however, data is
discarded until a start of packet is received after RAM power-up is completed. When 1, the Receive FIFO is
emptied, any transfer in progress is halted, the FIFO RAM is powered down, the RHDA bit is forced low, and all
incoming data is discarded.