FM25CL64B - 64Kb 3V SPI F-RAM

Document Number: 001-84477 Rev. *B

Page 8 of 17

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13-bit Address

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Figure 9. Memory Write (WREN not shown)

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Figure 10. Memory Read

Endurance

The FM25CL64B devices are capable of being

accessed at least 10

RAM memory operates with a read and restore

mechanism. Therefore, an endurance cycle is applied

on a row basis for each access (read or write) to the

memory array. The F-RAM architecture is based on

an array of rows and columns. Rows are defined by

A12-A3 and column addresses by A2-A0. See Block

Diagram (pg 2) which shows the array as 1K rows of

64-bits each. The entire row is internally accessed

once whether a single byte or all eight bytes are read

or written. Each byte in the row is counted only once

in an endurance calculation. The table below shows

endurance calculations for 64-byte repeating loop,

which includes an op-code, a starting address, and a

sequential 64-byte data stream. This causes each byte

to experience one endurance cycle through the loop.

F-RAM read and write endurance is virtually

unlimited even at 20MHz clock rate.

Table 5. Time to Reach Endurance Limit for Repeating 64-byte Loop

SCK Freq

(MHz)

Endurance

Cycles/sec.

Endurance

Cycles/year

Years to Reach

Limit

20

37,310

1.18 x 10

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85.1

10

18,660

5.88 x 10

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170.2

5

9,330

2.94 x 10

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340.3