LSI Logic Confidential
SDRAM Control and Clock Control Registers
13-13
Copyright © 2001, 2002 by LSI Logic Corporation. All rights reserved.
CAS L
6
CAS latency (tACK) specifies the minimum number
clocks between a read command and data being
returned. For SDR parts, the values are:
0 = 2 clocks
1 = 3 clocks
For DDR parts, the values are:
0 = 2.5 clocks
1 = 3 clocks.
Refresh Interval
[5:0]
Specifies the number of clocks between refresh cycle in
units of 64 clocks. Each refresh cycle will refresh all
banks of the DRAM. The nominal value for 150 MHz is
2340 clocks (2048 rows every 32 ms) for SDRAMs and
1170 clocks (1024 rows every 8 ms) for DDRs.
13.7 SDRAM Control and Clock Control Registers
As shown below, the SDRAM Control and Clock Control Registers in the
DMN-8600 processor set up the interface to SDRAM.
SDRAM Control Register
Cbus Address: 0x30000
Write Limit
[15:0]
A store by an incoming IPC target or any DMA transfer
to an DRAM address less than write limit * 4096 will
cause a DRAM Write Protection Interrupt to the RISC
core, and the write will be suppressed.
The SDRAM Clock Control Register controls the timing of the SDRAM
input and output clocks. This register must be written at least 1
31
16
Reserved
15
0
Write Limit