FM31278/276/274/272 - 5V I2C Companion

Rev. 2.0

Dec. 2007

Page 19 of 25

Figure 16. Selective (Random) Memory Read

Figure 17. Byte Register Write

Although not required, it is recommended that A5-A7 in the Register Address byte are zeros in order to

preserve compatibility with future devices.

Addressing F-RAM Array in the FM3127x Family

The FM3127x family includes 256Kb, 64Kb, 16Kb, and 4Kb memory densities. The following 2-byte address field

is shown for each density.

Table 4. Two-Byte Memory Address

Part #

FM31278

x

A14

A13

A12

A11

A10

A9

A8

A7

A6

A5

A4

A3

A2

A1

A0

FM31276

x

x

x

A12

A11

A10

A9

A8

A7

A6

A5

A4

A3

A2

A1

A0

FM31274

x

x

x

x

x

A10

A9

A8

A7

A6

A5

A4

A3

A2

A1

A0

FM31272

x

x

x

x

x

x

x

A8

A7

A6

A5

A4

A3

A2

A1

A0

S

A

Slave Address 1

Data Byte

1 P

By Master

By FM3127x

Start

Address

Stop

No

Acknowledge

Data

S

A

Slave Address 0

Address MSB

A

Start

Address

Acknowledge

Address LSB

A

S

A

Slave Address

0

Address

A

Data Byte

A

P

By Master

Start

Address & Data

Stop

Acknowledge

0 0 0

By FM3127x