W968D6DA Datasheet, PDF (24/75 Pages) Winbond – Low-power features

W968D6DA
256Mb Async./Page,Syn./Burst CellularRAM
8.4.2 Software Access
Software access of the registers uses a sequence of asynchronous READ and asynchronous WRITE operations.
The contents of the configuration registers can be modified and all registers can be read using the software
sequence.
The configuration registers are loaded using a four-step sequence consisting of two asynchronous READ operations
followed by two asynchronous WRITE operations. The read sequence is virtually identical except that an
asynchronous READ is performed during the fourth operation. The address used during all READ and WRITE
operations is the highest address of the CellularRAM device being accessed; the contents of this address are not
changed by using this sequence.
The data value presented during the third operation (WRITE) in the sequence defines whether the BCR, RCR, or the
DIDR is to be accessed. If the data is 0000h, the sequence will access the RCR; if the data is 0001h, the sequence
will access the BCR; if the data is 0002h, the sequence will access the DIDR. During the fourth operation, DQ[15:0]
transfer data into or out of bits 15–0 of the registers.
The use of the software sequence does not affect the ability to perform the standard (CRE-controlled) method of
loading the configuration registers. However, the software nature of this access mechanism eliminates the need for
CRE. If the software mechanism is used, CRE can simply be tied to VSS. The port line often used for CRE control
purposes is no longer required.
8.4.2.1 Load Configuration Register
ADDRESS
READ
Address
( MAX )
CE #
READ
Address
( MAX )
WRITE
Address
( MAX )
WRITE
Address
( MAX )
OE #
WE #
LB # / UB #
DATA
XXXXh
XXXXh
RCR : 0000h
BCR : 0001h
CR Value
In
Don‟t Care
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Publication Release Date : June 27, 2013
Revision : A01-003