PMC-Sierra, Inc.
PRELIMINARY
PM5381 S/UNI-2488
DATASHEET
PMC-2000489
ISSUE 1
SATURN USER NETWORK INTERFACE FOR 2488 MBIT/S
Register 076AH: RXSDQ FIFO Indirect Data Available Threshold
Bit
Type
Function
Default
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
DT[7]
DT[6]
0
0
0
0
0
0
1
1
X
X
X
0
0
0
1
1
DT[5]
DT[4]
DT[3]
DT[2]
DT[1]
Bit 8
DT[0]
Bit 7
Unused
Unused
Unused
Reserved
Reserved
Reserved
Reserved
Reserved
Bit 6
Bit 5
Bit 4
R/W
R/W
R/W
R/W
R/W
Bit 3
Bit 2
Bit 1
Bit 0
This register is used to set the Data Available Threshold for a FIFO. This threshold is explained in
the Operations Section. A FIFO does not need to be enabled to set this threshold. In order to
change this value for a FIFO, the user should first disable it, write in the new value, and enable it
again.
Reserved:
The Reserved bits should be set to their default values for proper operation.
DT[7:0]:
These bits specify the Data Available threshold for the FIFO selected by the RXSDQ FIFO
Indirect Address register’s PHYID[5:0] bits. When this threshold is being set, these bits are
written to by the user, and when this threshold is being read, these bits hold the previously
configured data. The threshold is equal to DT[7:0] + 1.
This threshold is set in 16 byte Blocks. This threshold can never be greater than the size of
the FIFO. The absolute maximum value is DT[7:0] +1 = 16. This number should be a
standard fraction of the FIFO size in blocks. In the case of ATM FIFOs, this number should
be set to a value of DT[7:0] = 3 (ATM cells are 4 Blocks long).
Proprietary and Confidentail to PMC-Sierra Inc., and for its Customer’s Internal Use
345
PMC [ PMC-SIERRA, INC ]
