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PM73487 QRT
PMC-Sierra, Inc.
PMC-980618
Issue 3
622 Mbps ATMTraffic Management Device
Released
Datasheet
237
APPENDIX C
RAM SELECTION
Table 49. QRT RAM Selection
NAME
Description
Type
Size
Suggested
RAMs
Interface
NOTES
AB_RAM
Contains head & tail
pointers and sent/drop
counters for RX queues
SSRAM
128kx18
MT58LC
128k18
D9-10
MT58LC
128k18
C6-10
17bit multiplex
bus.
See note “B”
AL_RAM
VPI/VCI Address Lookup
tables. Cell buffer pointers,
service order tables and
Multicast pointer FIFOs.
(Different ALRAM_CONFIG
modes correspond to
different VPI/VCI ranges
and cell buffer sizes)
SSRAM
128kx18
256kx18
*
512kx18
*
(see section 7.2.4
of the PM73487
Data Sheet )
1.
ALRAM_CONFIG
mode 0 = 64Kx18
2.
ALRAM_CONFIG
mode 1 = 128Kx 18
3.
ALRAM_CONFIG
mode 2 = 256Kx18
4.
ALRAM_CONFIG
mode 3 = 512Kx18
64kx36 = 4k VCs
128kx36 = 8k VCs
*
256kx36 = 16k VCs
*
MT58LC
128k18
D9-10
MT58LC
128k18
C6-10
MT58LC
256k18
D9-10
MT58LC
256k18
C6-10
17bit data, 18bit
address
See note “B”
Can use 2 256kx18
SCD chips by setting
ALRAM_TYPE = 1 (see
datasheet section 7.2.4)
CH_RAM
Per Tx/Rx channel table
info.
SSRAM
MT58LC
128k18
C6-10
MT58LC
256k18
C6-10
34bit data, 17bit
address
See note “B”
Rx DRAM
Receive cell buffers.
Per VC queuing.
64k cell buffers.
SDRAM
or
SGRAM
1Mx16 SDRAM *
256kx32 SGRAM
MT48LC
1M16
A1-10
(SDRAM)
MT41LC
256k32
D5-10
(SGRAM)
MT48LC
1M16
A1-10
(SDRAM)
32 bit data,
9bit address,
2bit CS.
SDRAM, must use 2
chips (64k cells).
SGRAM, can use 1 or 2
chips (16k or 32k cells).
Tx DRAM
Transmit cell buffers.
Per Virtual Output &
Service Class queuing.
64k cell buffers.
SDRAM
or
SGRAM
1Mx16 SDRAM *
256kx32 SGRAM
MT41LC
256k32
D5-10
(SGRAM)
32 bit data,
9bit address,
2bit CS.
SDRAM, must use 2
chips (64k cells).
SGRAM, can use 1 or 2
chips (16k or 32k cells).
*
Most common memory configurations.
Note “B” : SCD SSRAM can be used if the entire address space of the Ram bank is within 1 RAM chip.
SCD = Single Cycle Deselect memory. The notation ‘D9’ can be seen in the name of these SSRAM.
DCD = Double Cycle Deselect memory. The notation ‘C6’ can be seen in the name of these SSRAM.