FM32L278/L276/L274/L272 - 3V I2C Companion
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 =
D7
D6
D5
D4
D3
D2
D1
D0
Function
Range
FFh
FFh
FFh
FFh
FFh
FFh
FFh
FFh
FFh
FFh
FFh
FFh
Address
18h
17h
16h
15h
14h
13h
12h
11h
Serial Number Byte 7
Serial Number 7
Serial Number 6
Serial Number 5
Serial Number 4
Serial Number 3
Serial Number 2
Serial Number 1
Serial Number 0
Event Counter 2 MSB
Event Counter 2 LSB
Event Counter 1 MSB
Event Counter 1 LSB
Event Count Control
Companion Control
Serial Number Byte 6
Serial Number Byte 5
Serial Number Byte 4
Serial Number Byte 3
Serial Number Byte 2
Serial Number Byte 1
Serial Number Byte 0
Counter 2 MSB
10h
0Fh
0Eh
0Dh
0Ch
0Bh
0Ah
09h
00-08h
Counter 2 LSB
Counter 1 MSB
Counter 1 LSB
RC
CC
VBC
WDT2
WR2
C2P
-
WDT1
WR1
C1P
VTP
SNL
WDE
WTR
-
-
FC
-
LB
WP1
WDT4
-
WP0
WDT3
WR3
WDT0 Watchdog Control
WR0 Watchdog Restart/Flags
RESERVED
POR
DO NOT USE
*Note that the usable address range starts at address 09h to preserve software compatibility with the FM31L27x
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
18h
17h
16h
15h
14h
13h
12h
11h
0Bh
0Ah
Hex Value
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x1F
Rev. 3.0
Feb. 2009
Page 7 of 21
RAMTRON [ RAMTRON INTERNATIONAL CORPORATION ]
