MSM54V12222A datasheet(6/14 Pages) OKI | 262,214 Words x 12 Bits FIELD MEMORY

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OKI Semiconductor

MSM54V12222A

Read Operation

The read operation is controlled by tree clocks, SRCK, RSTR, and RE. Read operation is accomplished

by cycling SRCK and holding RE high after read address pointer reset operation or RSTR. Each read

operation, which begins after RSTR, must contain at least 80 active read cycles, i.e. SRCK cycles while

RE is high.

Read Reset : RSTR

The first positive transition of SRCK after RSTR going high resets the read address counters to zero.

RSTR setup and hold times are referenced to the rising edge of SRCK. Because the read reset function

is solely controlled by SRCK rising edge after high level of RSTR, the states of RE and RE are don't care

in the read reset cycle.

Before RSTR may be brought high again for a further reset operation, it must have been low for at least

*two SRCK cycles.

Data Out : Dout0-11

Read Clock : SRCK

Data is shifted out of the data registers triggered by the rising edge of SRCK when RE is high during a

read operation. The SRCK input increments the internal read address pointer when RE is high.

The three-state output buffer provides direct TTL compatibility ( no pullup resistor required). Data out is

the same polarity as data in. The output becomes valid after the access time interval tAC that begins with

the rising edge of SRCK. *There are no output valid time restriction on MSM54V12222A.

Read Enable : RE

The function of RE is gating of the SRCK clock, for incrementing the read pointer. When RE is high

before the rising edge of SRCK, the read pointer is incremented. When RE is low, the read pointer is not

incremented. RE setup times (tRENS and tRDSS) and RE hold times (tRENH and tRDSH) are refer-

enced to the rising edge of the SRCK clock.

Output Enable : OE

OE is used to enable/disable the outputs. OE high level enables the outputs. The internal read address

pointer is always incremented by cycling SRCK regardless of OE level. Note that OE setup and hold times

are referenced to the rising edge of SRCK.

MSM54V12222A Datasheet(PDF) 6 Page - OKI electronic componets