FM25V20 - 2Mb SPI F-RAM

Rev. 3.0

August 2012

Page 10 of 17

Endurance

The FM25V20 device is capable of being accessed at

least 10

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 A17-A3

and column addresses by A2-A0.

See Block

Diagram (pg 2) which shows the array as 32K 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 40MHz clock rate.

Table 6. Time to Reach 100 Trillion Cycles for Repeating 64-byte Loop

SCK Freq

(MHz)

Endurance

Cycles/sec.

Endurance

Cycles/year

Years to Reach

10

40

73,520

2.32 x 10

12

43.1

10

18,380

5.79 x 10

11

172.7

5

9,190

2.90 x 10

11

345.4