
Multi-Service Access Device For Channelized Interfaces
Telecom Standard Product Data Sheet
Production
Proprietary and Confidential to PMC-Sierra, Inc., and for its Customers’ Internal Use
Document ID: PMC-1990823, Issue 4
579
14.13 RXSDQ and TXSDQ FIFO Size Configuration
The SDQ supports 3 different FIFO sizes – 16 Blocks (equal to 4 ATM Cells or 256 bytes), 48
Blocks (equal to 12 ATM Cells or 768 bytes), and 192 Blocks (equal to 48 ATM Cells or 3072
bytes). Table 54 shows the recommended FIFO sizes for different data rates.
Table 54 Suggested FIFO Buffer Sizes
FIFO_BS[1:0]
FIFO Size (Blocks)
FIFO Size (Cells)
Suggested BW
00
Reserved
Reserved
Reserved
01
16
4
DS3/STS-1
10
48
12
STS-3c
11
192
48
STS-12c/48c
There are 768 Blocks (192 ATM Cells or 12288 bytes) of total storage that can be carved up into
a maximum of 48 FIFOs of the sizes mentioned above. The storage is organized in 4 banks of
192 Blocks each. Block numbers 0 to 191 (000H to 0BFH) are in Bank 0, 192 to 383 (0C0H to
17FH) are in Bank 1, 384 to 575 (180H to 23FH) are in Bank 2, and 576 to 767 (240H to 2FFH)
are in Bank 3.
In order to configure the SDQ, the user must first determine the size of each FIFO in Blocks, and
sum them. The total number of Blocks must be less than 768. The minimum FIFO size is 16
Blocks or 4 Cells. An additional restriction in the SDQ is that each of the four Banks of the SDQ
cannot contain more than 12 FIFOs of any size. Thus, if a user has configured 12 FIFOs of 8
Blocks each in Bank 0, then although only 96 of the possible 192 Blocks are used, no more can
be configured in this Bank.
The user then needs to program three things for a given FIFO PHYID (channel) –
The physical FIFO Number – the user can set up the FIFO in any one of the four available Banks.
The value of the FIFO_NUMBER[5:0] register bits (as specified in the FIFO Indirect
Configuration Register) must be set to correspond to the channel number (or equivalently, the
PHY number) as shown in Table 55.
Table 55 SDQ FIFO_NUMBER Configuration
Bank
UL3/PL3 Channel #
FIFO_NUMBER[5:0]
0
0 to 11
0 to 11 (0x00 to 0x0B)
1
12 to 23
16 to 27 (0x10 to 0x1B)
2
24 to 35
32 to 43 (0x20 to 0x2B)
3
36 to 47
48 to 59 (0x30 to 0x3B)
Note that the FIFO_NUMBER value must be set to correspond explicitly to the UL3/PL3
Channel #. For instance, for UL3/PL3 Channel #11, the FIFO_NUMBER must be set to the
value 11 (0x0B). For UL3/PL3 Channel #36, FIFO_NUMBER must be set to the value 48
(0x30). For UL3/PL3 Channel #25, FIFO_NUMBER must be set to the value 33 (0x21), and so
on for all the other UL3/PL3 Channel numbers.