emc646sp16ak Emlsi Inc., emc646sp16ak Datasheet - Page 21

• Manufacturer Part Number: emc646sp16ak
• Description: 4mx16 Bit Cellularram
• Manufacturer: Emlsi Inc.

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
LB#/UB#
LB#/UB#
Address
Address
DATA
DATA
OE#
WE#
OE#
WE#
CE#
CE#
ADDRESS
ADDRESS
READ
READ
XXXXh
XXXXh
Max
Max
ADDRESS
ADDRESS
XXXXh
XXXXh
READ
READ
Max
Max
21
RCR : 0000h
BCR : 0001h
RCR : 0000h
BCR : 0001h
DIDR : 0002h
ADDRESS
ADDRESS
WRITE
WRITE
Max
Max
CR Value Iout
CR Value In
ADDRESS
ADDRESS
WRITE
READ
Max
Max
EMC646SP16AK
Don’t Care
Don’t Care
4Mx16 CellularRAM