Functional Overview

Read data output by the memory device is also registered on the rising edge of

smc_mclk0n, equivalent to the falling edge of smc_mclk0, for asynchronous reads. For synchronous reads, read data is registered using the fed back clock, smc_fbclk_in. For synchronous and asynchronous accesses, the data is then pushed onto the read data FIFO to be returned by the SMC interface.

This subsection describes:

Asynchronous read

Asynchronous read in multiplexed-modeon page 2-29

Asynchronous write on page 2-30

Asynchronous write in multiplexed-modeon page 2-31

Asynchronous page mode read on page 2-31

Synchronous burst read on page 2-32

Synchronous burst read in multiplexed-modeon page 2-34

Synchronous burst write on page 2-35

Synchronous burst write in multiplexed-modeon page 2-36

Synchronous read and asynchronous write on page 2-37.

Asynchronous read

Table 2-2and Table 2-3list the smc_opmode0_<0-3> and SRAM Register settings. See Register summary on page 3-3.

Table 2-2 Asynchronous read opmode chip register settings

Field

mw

rd_sync rd_bl

wr_sync

wr_bl

baa

adv

bls

ba

 

 

 

 

 

 

 

 

 

 

 

Value

-

b0

b000

-

 

-

-

-

-

-

 

 

 

 

 

Table 2-3 Asynchronous read SRAM cycles register settings

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Field

t_rc

t_wc

t_ceoe

 

t_wp

t_pc

t_tr

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Value

b0011

-

b001

 

-

-

-

 

 

 

 

 

 

 

 

 

 

 

Figure 2-14 on page 2-29shows a single asynchronous read transfer with an initial access time, tRC, of three cycles and an output enable assertion delay, tCEOE, of one cycle.

2-28

Copyright © 2006 ARM Limited. All rights reserved.

ARM DDI 0389B

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Image 48
SMC Networks PL241 manual Asynchronous read opmode chip register settings, Asynchronous read Sram cycles register settings