FM22L16 datasheet(7/15 Pages) RAMTRON

7 / 15 page

FM22L16

Rev. 1.0

Mar. 2007

Page 7 of 15

Software Write Protect Timing

SRAM Drop-In Replacement

The FM22L16 has been designed to be a drop-in

replacement for standard asynchronous SRAMs. The

device does not require /CE to toggle for each new

address. /CE may remain low indefinitely. While /CE

is low, the device automatically detects address

changes and a new access is begun. This functionality

allows /CE to be grounded as you might with an

SRAM. It also allows page mode operation at speeds

up to 40MHz. Note that if /CE is tied to ground,

the user must be sure /WE is not low at powerup

or powerdown events. If /CE and /WE are both

low during power cycles, data corruption will

occur.

For applications that require the lowest power

consumption, the /CE signal should be active only

during memory accesses. The FM22L16 draws IDD

supply current while /CE is low, even if addresses and

control signals are static. While /CE is high, the

device draws no more than the maximum standby

current ISB.

The FM22L16 is backward compatible with the

1Mbit FM20L08 and 256Kbit FM18L08 devices.

That is, operating the FM22L16 with /CE toggling

low on every address is perfectly acceptable.

The /UB and /LB byte select pins are active for both

read and write cycles. They may be used to allow the

device to be wired as a 512Kx8 memory. The upper

and lower data bytes can be tied together and

controlled with the byte selects. Individual byte

enables or the next higher address line A(18) may be

available from the system processor.

Figure 3. FM22L16 Wired as 512Kx8

FM22L16 Datasheet(PDF) 7 Page - Ramtron International Corporation