FEDS54V12222B-01

OKI Semiconductor

MSM54V12222B

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Read Operation

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

cycling SRCK, and holding RE high after the read address pointer reset operation or RSTR.

Each read operation, which begins after RSTR, must contain at least 150 active read cycles, i.e. SRCK cycles while

RE is high.

Read Reset: RSTR

The first positive transition of SRCK after RSTR becomes 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 the SRCK rising edge after the high level of RSTR, the states of RE and OE are ignored in the read reset cycle.

Before RSTR may be brought high again for a further reset operation, it must be low for at least *two SRCK

cycles.

Read Clock: SRCK

Data is shifted out of the data registers. It is 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

SRCK. *There are no output valid time restriction on MSM54V12222B.

Read Enable: RE

The function of RE is to gate 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

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 the OE level. Note that OE setup and hold times are referenced

to the rising edge of SRCK.