FM32278/276/274/272 - 5V I2C Companion

Rev. 3.0

Feb. 2009

Page 7 of 21

Register Map

The processor companion functions are accessed via 16 special function registers mapped to a separate 2-wire

device ID. The interface protocol is described below. The registers contain timekeeping data, control bits, or

information flags. A description of each register follows the summary table below.

Register Map Summary Table

Nonvolatile =

Battery-backed =

Address

D7

D6

D5

D4

D3

D2

D1

D0

Function

Range

Serial Number Byte 7

Serial Number 7

FFh

Serial Number Byte 6

Serial Number 6

FFh

Serial Number Byte 5

Serial Number 5

FFh

Serial Number Byte 4

Serial Number 4

FFh

Serial Number Byte 3

Serial Number 3

FFh

Serial Number Byte 2

Serial Number 2

FFh

Serial Number Byte 1

Serial Number 1

FFh

Serial Number Byte 0

Serial Number 0

FFh

10h

Counter 2 MSB

Event Counter 2 MSB

FFh

0Fh

Counter 2 LSB

Event Counter 2 LSB

FFh

0Eh

Counter 1 MSB

Event Counter 1 MSB

FFh

0Dh

Counter 1 LSB

Event Counter 1 LSB

FFh

0Ch

RC

CC

C2P

C1P

Event Count Control

0Bh

SNL

-

FC

WP1

WP0

VBC

-

VTP

Companion Control

0Ah

WDE

-

-

WDT4

WDT3

WDT2

WDT1

WDT0

Watchdog Control

09h

WTR

POR

LB

-

WR3

WR2

WR1

WR0

Watchdog Restart/Flags

00-08h

RESERVED

DO NOT USE

18h

17h

11h

16h

15h

14h

13h

12h

*Note that the usable address range starts at address 09h to preserve software compatibility with the FM3127x

device family, which includes a real-time clock in registers 00-08h.

Note: When the device is first powered up and programmed, all registers must be written because the battery-

backed register values cannot be guaranteed. The table below shows the default values of the non-volatile

registers. All other register values should be treated as unknown.

Default Register Values

Address

Hex Value

18h

0x00

17h

0x00

16h

0x00

15h

0x00

14h

0x00

13h

0x00

12h

0x00

11h

0x00

0Bh

0x00

0Ah

0x1F