FM33256B SPI Companion w/ FRAM

This product conforms to specifications per the terms of the Ramtron

Ramtron International Corporation

standard warranty. The product has completed Ramtron’s internal

1850 Ramtron Drive, Colorado Springs, CO 80921

qualification testing and has reached production status.

(800) 545-FRAM, (719) 481-7000

www.ramtron.com

Rev. 3.0

Aug. 2012

Page 13 of 28

Register Map

The RTC and processor companion functions are accessed via 30 special function registers, which are mapped to

unique op-codes. The interface protocol is described on page 18. The registers contain timekeeping data, alarm

settings, control bits, and information flags. A description of each register follows the summary table.

Register Map Summary Table

Battery-backed =

Nonvolatile =

BB/NV User Programmable =

Address

D7

D6

D5

D4

D3

D2

D1

D0

Function

Range

/Match

0

0

10 mo

Alarm months

Alarm Month

01-12

/Match

0

10 date

Alarm date

Alarm Date

01-31

/Match

0

Alarm 10 hours

Alarm hours

Alarm Hours

00-23

/Match

Alarm 10 minutes

Alarm minutes

Alarm Minutes

00-59

/Match

Alarm 10 seconds

Alarm seconds

Alarm Seconds

00-59

SNL

AL/SW

F1

F0

VBC

FC

VTP1

VTP0

Companion Control

Serial Number 7

FFh

Serial Number 6

FFh

Serial Number 5

FFh

Serial Number 4

FFh

Serial Number 3

FFh

Serial Number 2

FFh

Serial Number 1

FFh

Serial Number 0

FFh

Event Counter Byte 1

Event Counter 1

FFh

Event Counter Byte 0

Event Counter 0

FFh

NVC

-

-

-

RC

WC

POLL

CP

Event Counter Control

0Ch

WDE

-

-

WDSET4

WDET3

WDET2

WDET1

WDET0

Watchdog Control

0Bh

-

-

-

WDST4

WDST3

WDST2

WDST1

WDST0

Watchdog Control

0Ah

-

-

-

-

WR3

WR2

WR1

WR0

Watchdog Restart

09h

EWDF

LWDF

POR

LB

-

-

-

-

Watchdog Flags

08h

10 years

years

Years

00-99

07h

0

0

0

10 mo

months

Month

01-12

06h

0

0

10 date

date

Date

01-31

05h

0

0

0

0

0

Day

01-07

04h

0

0

10 hours

hours

Hours

00-23

03h

0

10 minutes

minutes

Minutes

00-59

02h

0

10 seconds

seconds

Seconds

00-59

01h

-

-

CALS

CAL4

CAL3

CAL2

CAL1

CAL0

CAL/Control

00h

/OSCEN

AF

CF

AEN

reserved

CAL

W

R

RTC/Alarm Control

0Eh

Serial Number Byte 1

Serial Number Byte 0

1Ah

19h

10h

1Dh

1Ch

1Bh

day

Serial Number Byte 7

Serial Number Byte 6

Serial Number Byte 5

Serial Number Byte 4

Serial Number Byte 3

Serial Number Byte 2

0Dh

0Fh

18h

16h

17h

11h

13h

14h

15h

12h

Note: When the device is first powered up and programmed, all timekeeping 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 and some of

the battery-backed bits. All other register values should be treated as unknown

.

Default Register Values

Address

Hex Value

Address

Hex Value

1Dh

0x81

12h

0x00

1Ch

0x81

11h

0x00

1Bh

0x80

10h

0x00

1Ah

0x80

0Fh

0x00

19h

0x80

0Eh

0x00

18h

0x40

0Dh

0x01

17h

0x00

0Ch

0x00

16h

0x00

0Bh

0x00

15h

0x00

01h

0x00

14h

0x00

00h

0x80

13h

0x00