PM5380-BI PMC-Sierra, Inc., PM5380-BI Datasheet - Page 316

• Manufacturer Part Number: PM5380-BI
• Description: Network Interface, SATURN User Network Interface (8x155) Telecom Standard Product
• Manufacturer: PMC-Sierra, Inc.

Proprietary and Confidential to PMC-Sierra, Inc., and for its customers’ internal use.
Document No.: PMC- 2010299, Issue 2
Register 0x1013: TUL3 ATM Level 3 FIFO Configuration
FIFODP[1:0]:
CELLFORM:
The FIFODP[1:0] bits determine the channel FIFO level at which TCA deasserts in
UTOPIA Level 3 operation. FIFO fill level control may be important in systems where the
cell latency through the TUL3-32 must be minimized or when the layer device latency of
deasserting TENB is large.
When the channel FIFO is filled to the specified depth, the transmit cell available signal
TCA is deasserted. When the FIFO fill level is set below the maximum size of the channel
FIFO, the channel FIFO will still accept writes. TCA is asserted when the FIFO depth falls
below the level specified by FIFODP[1:0].
FIFODP[1:0] specifies the FIFO full level in number of ATM cells, plus one, in the channel
FIFO. Therefore, the FIFO full level may be configured from 1 to 4 ATM cells.
The CELLFORM bits controls the length of transmit Level 3 interface ATM cell structure.
When CELLFORM is low, the ATM cell structure is 56 bytes in size (14 TFCLK cycles)
and contains the HCS (H5) and HCS Control bytes. When CELLFORM is high, the ATM
cell structure is 52 bytes in size (13 TFCLK cycles) and does not contain the HCS and HCS
Control bytes.
The value of CELLFORM should be changed only when FIFORST is set high.
Bit
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Type
R/W
R/W
R/W
R/W
R/W
Function
CELLFORM
Unused
Unused
Unused
Reserved
Reserved
FIFODP[1]
FIFODP[0]
S/UNI®-8x155 ASSP Telecom Standard Product Data Sheet
Default
0
X
X
X
0
0
1
1
Released
316