Released
Datasheet
PM73487 QRT
PMC-Sierra, Inc.
PMC-980618
Issue 3
622 Mbps ATM Traffic Management Device
APPENDIX C RAM SELECTION
Table 49. QRT RAM Selection
Suggested
RAMs
NAME
Description
Type
Size
Interface
NOTES
Contains head & tail
pointers and sent/drop
counters for RX queues
MT58LC128k18D9-10
MT58LC128k18C6-10
17bit multiplex
bus.
SSRAM
128kx18
See note “B”
AB_RAM
128kx18
256kx18*
512kx18*
VPI/VCI Address Lookup
tables. Cell buffer pointers,
service order tables and
Multicast pointer FIFOs.
(see section 7.2.4
of the PM73487
Data Sheet )
1. ALRAM_CONFIG
mode 0 = 64Kx18
See note “B”
MT58LC128k18D9-10
MT58LC128k18C6-10
MT58LC256k18D9-10
MT58LC256k18C6-10
Can use 2 256kx18
SCD chips by setting
ALRAM_TYPE = 1 (see
datasheet section 7.2.4)
17bit data, 18bit
address
SSRAM
AL_RAM
(Different ALRAM_CONFIG
modes correspond to
different VPI/VCI ranges
and cell buffer sizes)
2. ALRAM_CONFIG
mode 1 = 128Kx 18
3. ALRAM_CONFIG
mode 2 = 256Kx18
4. ALRAM_CONFIG
mode 3 = 512Kx18
64kx36 = 4k VCs
Per Tx/Rx channel table
info.
MT58LC128k18C6-10
MT58LC256k18C6-10
34bit data, 17bit
address
SSRAM
128kx36 = 8k VCs*
256kx36 = 16k VCs*
See note “B”
CH_RAM
Rx DRAM
MT48LC1M16A1-10
SDRAM, must use 2
chips (64k cells).
SGRAM, can use 1 or 2
chips (16k or 32k cells).
Receive cell buffers.
Per VC queuing.
64k cell buffers.
SDRAM
or
SGRAM
1Mx16 SDRAM *
256kx32 SGRAM
(SDRAM)
32 bit data,
9bit address,
2bit CS.
MT41LC256k32D5-10
(SGRAM)
MT48LC1M16A1-10
(SDRAM)
Transmit cell buffers.
Per Virtual Output &
Service Class queuing.
64k cell buffers.
SDRAM, must use 2
chips (64k cells).
SGRAM, can use 1 or 2
chips (16k or 32k cells).
SDRAM
or
SGRAM
1Mx16 SDRAM *
256kx32 SGRAM
32 bit data,
9bit address,
2bit CS.
Tx DRAM
MT41LC256k32D5-10
(SGRAM)
* 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.
237
PMC [ PMC-SIERRA, INC ]
