EMC646SP16JS-12LL datasheet(21/65 Pages) EMLSI

21 / 65 page

EMC646SP16J

4Mx16 CellularRAM

Preliminary

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.(See Figure 14.) The read sequence is virtually identical except that an asynchronous READ is performed during the fourth

operation. (See Figure 15.) The address used during all READ and WRITE operations is the highest address of the CellularRAM device

being accessed (3FFFFFh); 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 in to 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.

Figure 14: Load Configuration Register

Figure 15: Read Configuration Register

Address

CE#

OE#

WE#

LB#/UB#

DATA

ADDRESS

Max

ADDRESS

Max

ADDRESS

Max

ADDRESS

Max

XXXXh

RCR : 0000h

BCR : 0001h

CR Value In

Don’t Care

READ

WRITE

Address

CE#

OE#

WE#

LB#/UB#

DATA

ADDRESS

Max

ADDRESS

Max

ADDRESS

Max

ADDRESS

Max

XXXXh

RCR : 0000h

BCR : 0001h

CR Value out

Don’t Care

READ

WRITE

READ

DIDR : 0002h

EMC646SP16JS-12LL Datasheet(PDF) 21 Page - Emerging Memory & Logic Solutions Inc

EMC646SP16JS-12LL Datasheet(HTML) 21 Page - Emerging Memory & Logic Solutions Inc

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