S D R A M

Command

CSx_

A13:0

CAS3_ RAS#

CAS2_ CAS#

CAS1_ WE#

CAS0_ A10/AP

 

 

 

 

 

 

 

Load mode

0

Op-code

0

0

0

0

 

 

 

 

 

 

 

Table 45: SDRAM command definitions

Memory timing fields — SDRAM

The WAIT configuration in the Chip Select Option register provides the SDRAM TRCD and TRP parameters. When WAIT is configured with a value of 0, the active and precharge commands can be followed immediately by another command on the next active edge of BCLK. When WAIT is configured with a value larger than 0, wait states are inserted after the active and precharge commands before another command can be issued.

The BCYC configuration in the Chip Select Option register provides the SDRAM CAS latency parameter. The BCYC field must be set to a value of CAS latency - 1. The NS7520 can support SDRAMs that have a CAS latency specification between 1 and 4 BCLK clocks, as shown:

CAS latency BCYC configuration

100

201

310

411

BSIZE configuration

The BSIZE configuration in the Chip Select Option register provides the SDRAM burst length parameter. The BSIZE field is set as shown:

BSIZE

Burst length

 

 

002 words (not supported)

014 words (not supported)

108 words (not supported)

1 1 8

N S 7 5 2 0 H a r d w a r e R e f e r e n c e , R e v . D 0 3 / 2 0 0 6

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Image 132
Digi NS7520 manual Memory timing fields Sdram, Bsize configuration, CAS latency Bcyc configuration, Burst length