RAMTRON FM32274

FM32278/276/274/272
5V Integrated Processor Companion with Memory
Features
High Integration Device Replaces Multiple Parts
• Serial Nonvolatile Memory
• Low Voltage Reset
• Watchdog Timer
• Early Power-Fail Warning/NMI
• Two 16-bit Event Counters
• Serial Number with Write-lock for Security
Processor Companion
• Active-low Reset Output for VDD and Watchdog
• Programmable VDD Reset Trip Point
• Manual Reset Filtered and Debounced
• Programmable Watchdog Timer
• Dual Battery-backed Event Counter Tracks
System Intrusions or other Events
• Comparator for Early Power-Fail Interrupt
• 64-bit Programmable Serial Number with Lock
Description
The FM3227x is a family of integrated devices that
includes the most commonly needed functions for
processor-based systems. Major features include
nonvolatile memory available in various sizes, lowVDD reset, watchdog timer, nonvolatile event
counter, lockable 64-bit serial number area, and
general purpose comparator that can be used for an
early power-fail (NMI) interrupt or other purpose.
The family operates from 4.0 to 5.5V.
The FM3227x family is software and pinout
compatible with the FM3127x family which also
includes a real-time clock. The common features
allow a system design that easily can be assembled
with or without timekeeping by simply selecting the
FM3127x or FM3227x, respectively.
Each FM3227x provides nonvolatile RAM available
in sizes including 4Kb, 16Kb, 64Kb, and 256Kb
versions. Fast write speed and unlimited endurance
allow the memory to serve as extra RAM or
conventional nonvolatile storage. This memory is
truly nonvolatile rather than battery backed.
This product conforms to specifications per the terms of the Ramtron
standard warranty. The product has completed Ramtron’s internal
qualification testing and has reached production status.
Rev. 3.0
Feb. 2009
Ferroelectric Nonvolatile RAM
• 4Kb, 16Kb, 64Kb, and 256Kb versions
• Unlimited Read/Write Endurance
• 45 year Data Retention
• NoDelay™ Writes
Fast Two-wire Serial Interface
• Up to 1 MHz Maximum Bus Frequency
• Supports Legacy Timing for 100 kHz & 400 kHz
• Device Select Pins for up to 4 Memory Devices
• Companion Controlled via 2-wire Interface
Easy to Use Configurations
• Operates from 4.0 to 5.5V
• 14-pin “Green”/RoHS SOIC package (-G)
• Pin Compatible with FM3127x Series
• Low Operating Current
• -40°C to +85°C Operation
• Underwriters Laboratory (UL) Recognized
The processor companion includes commonly needed
CPU support functions. Supervisory functions
include a reset output signal controlled by either a
low VDD condition or a watchdog timeout. /RST
goes active when VDD drops below a programmable
threshold and remains active for 100 ms after VDD
rises above the trip point. A programmable watchdog
timer runs from 100 ms to 3 seconds. The watchdog
timer is optional, but if enabled it will assert the reset
signal for 100 ms if not restarted by the host before
the timeout. A flag-bit indicates the source of the
reset.
A general-purpose comparator compares an external
input pin to the onboard 1.2V reference. This is
useful for generating a power-fail interrupt (NMI) but
can be used for any purpose. The family also includes
a programmable 64-bit serial number that can be
locked making it unalterable.
Additionally the FM3227x offers a dual event
counter that tracks the number of rising or falling
edges detected on dedicated input pins. The counter
can optionally be battery backed and even battery
operated by attaching a backup power source to the
VBAK pin. If VBAK is connected to a battery or
capacitor, then events will be counted even in the
absence of VDD.
Ramtron International Corporation
1850 Ramtron Drive, Colorado Springs, CO 80921
(800) 545-FRAM, (719) 481-7000
http://www.ramtron.com
Page 1 of 21
FM32278/276/274/272 - 5V I2C Companion
Pin Configuration
CNT1
1
14
VDD
CNT2
2
13
SCL
A0
3
12
SDA
A1
4
11
NC
PFO
5
10
NC
RST
6
9
PFI
VSS
7
8
VBAK
Pin Name
CNT1, CNT2
A0, A1
PFO
/RST
PFI
SDA
SCL
VBAK
VDD
VSS
Function
Event Counter Inputs
Device Select inputs
Early Power-Fail Output
Reset Input/Output
Early Power-fail Input
Serial Data
Serial Clock
Battery-Backup Supply
Supply Voltage
Ground
Ordering Information
Base Configuration
FM32278
FM32276
FM32274
FM32272
Memory Size
256Kb
256Kb
64Kb
64Kb
16Kb
16Kb
4Kb
4Kb
Operating Voltage
4.0-5.5V
4.0-5.5V
4.0-5.5V
4.0-5.5V
4.0-5.5V
4.0-5.5V
4.0-5.5V
4.0-5.5V
Reset Threshold
3.9, 4.4V
3.9, 4.4V
3.9, 4.4V
3.9, 4.4V
3.9, 4.4V
3.9, 4.4V
3.9, 4.4V
3.9, 4.4V
Ordering Part Number
FM32278-G
FM32278-GTR (tape&reel)
FM32276-G
FM32276-GTR (tape&reel)
FM32274-G
FM32274-GTR (tape&reel)
FM32272-G
FM32272-GTR (tape&reel)
Other memory configurations may be available. Please contact the factory for more information.
Rev. 3.0
Feb. 2009
Page 2 of 21
FM32278/276/274/272 - 5V I2C Companion
SCL
2-Wire
Interface
SDA
LockOut
A1, A0
FRAM
Array
LockOut
RST
Watchdog
Special
Function
Registers
LV Detect
S/N
PFI
Event
Counters
+
PFO
2.5V
1.2V
CNT1
CNT2
+
VDD
Switched Power
VBAK
Nonvolatile
Battery Backed
Figure 1. Block Diagram
Pin Descriptions
Pin Name
A0, A1
Type
Input
CNT1,
CNT2
Input
PFO
/RST
SDA
Output
I/O
I/O
SCL
Input
PFI
Input
VBAK
Supply
VDD
VSS
Supply
Supply
Rev. 3.0
Feb. 2009
Pin Description
Device select inputs are used to address multiple memories on a serial bus. To select the
device the address value on the two pins must match the corresponding bits contained in
the device address. The device select pins are pulled down internally.
Event Counter Inputs: These battery-backed inputs increment counters when an edge is
detected on the corresponding CNT pin. The polarity is programmable. These pins
should not be left floating. Tie to ground if pins are not used.
Power Fail Output: This is the early power-fail output.
Active low reset output with weak pull-up. Also input for manual reset.
Serial Data & Address: This is a bi-directional line for the two-wire interface. It is opendrain and is intended to be wire-OR’d with other devices on the two-wire bus. The input
buffer incorporates a Schmitt trigger for noise immunity and the output driver includes
slope control for falling edges. A pull-up resistor is required.
Serial Clock: The serial clock line for the two-wire interface. Data is clocked out of the
part on the falling edge, and in on the rising edge. The SCL input also incorporates a
Schmitt trigger input for noise immunity.
Early Power-fail Input: Typically connected to an unregulated power supply to detect an
early power failure. This pin should not be left floating.
Backup supply voltage: A 3V battery or a large value capacitor. If no backup supply is
used, this pin should be tied to ground and the VBC bit should be cleared. The trickle
charger is UL recognized and ensures no excessive current when using a lithium battery.
Supply Voltage
Ground
Page 3 of 21
FM32278/276/274/272 - 5V I2C Companion
Overview
The FM3227x family combines a serial nonvolatile
RAM with a processor companion. The companion is
a highly integrated peripheral including a processor
supervisor, a comparator used for early power-fail
warning, nonvolatile event counters, and a 64-bit
serial number. The FM3227x integrates these
complementary but distinct functions that share a
common interface in a single package. Although
monolithic, the product is organized as two logical
devices, the F-RAM memory and the companion.
From the system perspective they appear to be two
separate devices with unique IDs on the serial bus.
The FM3227x provides the same functions as the
FM3127x with the exception of the real-time clock.
This makes it easy to develop a common design that
can either include timekeeping by using the
FM3127x or exclude it by using the FM3227x. All
other features are identical. The register address map
is even preserved so that software can be identical.
The memory is organized as a stand-alone 2-wire
nonvolatile memory with a standard device ID value.
The companion functions are accessed under their
own 2-wire device ID. This allows the companion
functions to be read while maintaining the most
recently used memory address. The companion
functions are controlled by 16 special function
registers. The event counter circuits and related
registers are maintained by the power source on the
VBAK pin, allowing them to operate from battery or
backup capacitor power when VDD drops below a set
threshold. Each functional block is described below.
Memory Operation
The FM3227x is a family of products available in
different memory sizes including 4Kb, 16Kb, 64Kb,
and 256Kb. The family is software compatible, all
versions use consistent two-byte addressing for the
memory device. This makes the lowest density
device different from its stand-alone memory
counterparts but makes them compatible within the
entire family.
Memory is organized in bytes, for example the 4Kb
memory is 512 x 8 and the 256Kb memory is 32,768
x 8. The memory is based on F-RAM technology.
Therefore it can be treated as RAM and is read or
written at the speed of the two-wire bus with no
delays for write operations. It also offers effectively
unlimited write endurance unlike other nonvolatile
memory technologies. The 2-wire interface protocol
is described further on page 13.
The memory array can be write-protected by
software. Two bits in the processor companion area
Rev. 3.0
Feb. 2009
(WP0, WP1 in register 0Bh) control the protection
setting as shown in the following table. Based on the
setting, the protected addresses cannot be written and
the 2-wire interface will not acknowledge any data to
protected addresses. The special function registers
containing these bits are described in detail below.
Write protect addresses
None
Bottom 1/4
Bottom 1/2
Full array
WP1
0
0
1
1
WP0
0
1
0
1
Processor Companion
In addition to nonvolatile RAM, the FM3227x family
incorporates a highly integrated processor
companion. It includes a low voltage reset, a
programmable watchdog timer, battery-backed event
counters, a comparator for early power-fail detection
or other purposes, and a 64-bit serial number.
Processor Supervisor
Supervisors provide a host processor two basic
functions: detection of power supply fault conditions
and a watchdog timer to escape a software lockup
condition. All FM3227x devices have a reset pin
(/RST) to drive the processor reset input during
power faults (and power-up) and software lockups. It
is an open drain output with a weak internal pull-up
to VDD. This allows other reset sources to be wireOR’d to the /RST pin. When VDD is above the
programmed trip point, /RST output is pulled weakly
to VDD. If VDD drops below the reset trip point
voltage level (VTP) the /RST pin will be driven low. It
will remain low until VDD falls too low for circuit
operation which is the VRST level. When VDD rises
again above VTP, /RST will continue to drive low for
at least 100 ms (tRPU) to ensure a robust system reset
at a reliable VDD level. After tRPU has been met, the
/RST pin will return to the weak high state. While
/RST is asserted, serial bus activity is locked out even
if a transaction occurred as VDD dropped below VTP.
A memory operation started while VDD is above VTP
will be completed internally.
Figure 2 below illustrates the reset operation in
response to the VDD voltage.
VDD
tRPU
VTP
RST
Figure 2. Low Voltage Reset
Page 4 of 21
FM32278/276/274/272 - 5V I2C Companion
The bit VTP controls the trip point of the low voltage
detect circuit. It is located in register 0Bh, bit 0. Note
that the bit 1 location is a “don’t care”.
VTP
3.9V
4.4V
VTP
0
1
The watchdog timer can also be used to assert the
reset signal (/RST). The watchdog is a free running
programmable timer. The period can be software
programmed from 100 ms to 3 seconds in 100 ms
increments via a 5-bit nonvolatile register. All
programmed settings are minimum values and vary
with temperature according to the operating
specifications. The watchdog has two additional
controls associated with its operation, a watchdog
enable bit (WDE) and timer restart bits (WR). Both
the enable bit must be set and the watchdog must
timeout in order to drive /RST active. If a reset event
occurs, the timer will automatically restart on the
rising edge of the reset pulse. If WDE=0, the
watchdog timer runs but a watchdog fault will not
cause /RST to be asserted low. The WTR flag will be
set, indicating a watchdog fault. This setting is useful
during software development and the developer does
not want /RST to drive. Note that setting the
maximum timeout setting (11111b) disables the
counter to save power. The second control is a nibble
that restarts the timer preventing a reset. The timer
should be restarted after changing the timeout value.
The watchdog timeout value is located in register
0Ah, bits 4-0, and the watchdog enable is bit 7. The
watchdog is restarted by writing the pattern 1010b to
the lower nibble of register 09h. Writing this pattern
will also cause the timer to load new timeout values.
Writing other patterns to this address will not affect
its operation. Note the watchdog timer is freerunning. Prior to enabling it, users should restart the
timer as described above. This assures that the full
timeout period will be set immediately after enabling.
The watchdog is disabled when VDD is below VTP.
The following table summarizes the watchdog bits.
Watchdog timeout
Watchdog enable
Watchdog restart
100 ms
clock
Timebase
WDT4-0
WDE
WR3-0
MCU
RST
FM3227x
Reset
Switch
Switch
Behavior
FM3227x
drives
RST
100 ms (min.)
Figure 4. Manual Reset
Note that an internal weak pull-up on /RST
eliminates the need for additional external
components.
Reset Flags
In case of a reset condition, a flag will be set to
indicate the source of the reset. A low VDD reset or
manual reset is indicated by the POR flag, register
09h bit 6. A watchdog reset is indicated by the WTR
flag, register 09h bit 7. Note that the flags are
internally set in response to reset sources, but they
must be cleared by the user. When the register is
read, it is possible that both flags are set if both have
occurred since the user last cleared them.
Early Power Fail Comparator
An early power fail warning can be provided to the
processor well before VDD drops out of spec. The
comparator is used to create a power fail interrupt
(NMI). This can be accomplished by connecting the
PFI pin to the unregulated power supply via a resistor
divider. An application circuit is shown below.
Regulator
VDD
0Ah, bits 4-0
0Ah, bit 7
09h, bits 3-0
FM3227x
WR3-0 = 1010b to restart
Counter
Watchdog
timeout
/RST
PFI
To MCU
NMI input
PFO
+
-
1.2V ref
WDE
Figure 3. Watchdog Timer
Rev. 3.0
Feb. 2009
Manual Reset
The /RST pin is bi-directional and allows the
FM3227x to filter and de-bounce a manual reset
switch. The /RST input detects an external low
condition and responds by driving the /RST signal
low for 100 ms.
Figure 5. Comparator as Early Power-Fail Warning
Page 5 of 21
FM32278/276/274/272 - 5V I2C Companion
The voltage on the PFI input pin is compared to an
onboard 1.2V reference. When the PFI input voltage
drops below this threshold, the comparator will drive
the PFO pin to a low state. The comparator has 100
mV (max) of hysteresis to reduce noise sensitivity,
only for a rising PFI signal. For a falling PFI edge,
there is no hysteresis.
The comparator is a general purpose device and its
application is not limited to the NMI function.
Note: The maximum voltage on the comparator input PFI
is limited to 3.75V under normal operating conditions.
Event Counter
The FM3227x offers the user two battery-backed
event counters. Input pins CNT1 and CNT2 are
programmable edge detectors. Each clocks a 16-bit
counter. When an edge occurs, the counters will
increment their respective registers. Counter 1 is
located in registers 0Dh and 0Eh, Counter 2 is
located in registers 0Fh and 10h. These register
values can be read anytime VDD is above VTP, and
they will be incremented as long as a valid VBAK
power source is provided. To read, set the RC bit
register 0Ch bit 3 to 1. This takes a snapshot of all
four counter bytes allowing a stable value even if a
count occurs during the read. The registers can be
written by software allowing the counters to be
cleared or initialized by the system. Counts are
blocked during a write operation. The two counters
can be cascaded to create a single 32-bit counter by
setting the CC control bit (register 0Ch). When
cascaded, the CNT1 input will cause the counter to
increment. CNT2 is not used in this mode.
C1P
16-bit Counter
CNT1
C2P
CNT2
16-bit Counter
CC
Figure 6. Event Counter
The control bits for event counting are located in
register 0Ch. Counter 1 Polarity is bit C1P, bit 0;
Counter 2 Polarity is C2P, bit 1; the Cascade Control
is CC, bit 2; and the Read Counter bit is RC bit 3.
The polarity bits must be set prior to setting the
counter value(s). If a polarity bit is changed, the
counter may inadvertently increment. If the counter
pins are not being used, tie them to ground.
Rev. 3.0
Feb. 2009
Serial Number
A memory location to write a 64-bit serial number is
provided. It is a writeable nonvolatile memory block
that can be locked by the user once the serial number
is set. The 8 bytes of data and the lock bit are all
accessed via the device ID for the processor
companion. Therefore the serial number area is
separate and distinct from the memory array. The
serial number registers can be written an unlimited
number of times, so these locations are general
purpose memory. However once the lock bit is set the
values cannot be altered and the lock cannot be
removed. Once locked the serial number registers can
still be read by the system.
The serial number is located in registers 11h to 18h.
The lock bit is SNL, register 0Bh bit 7. Setting the
SNL bit to a 1 disables writes to the serial number
registers, and the SNL bit cannot be cleared.
Backup Power
The event counter and battery-backed registers may
be powered with a backup power source. When the
primary system power fails, the voltage on the VDD
pin will drop. When VDD is less than 2.5V, the event
counters and battery-backed registers will switch to
the backup power supply on VBAK.
A battery may be inserted into a system board
without any concern for excessive current draw on
the FM3227x’s VBAK pin.
Trickle Charger
To facilitate capacitor backup, the VBAK pin can
optionally provide a trickle charge current. When the
VBC bit, register 0Bh bit 2, is set to ‘1’, the VBAK pin
will source approximately 80 µA until VBAK reaches
3.75V. In 5V systems, this charges the capacitor to
VDD without an external diode and resistor charger
and also prevents the user from exceeding the VBAK
maximum voltage specification. There is a Fast
Charge mode which is enabled by the FC bit (register
0Bh, bit 5). In this mode the trickle charger current is
set to approximately 1 mA, allowing a large backup
capacitor to charge more quickly.
In the case where no backup source is used, the VBAK
pin should be tied to VSS. VBAK should not be tied to
5V since the VBAK (max) specification will be
exceeded. Be sure to turn off the trickle charger
(VBC=0), otherwise charger current will be shunted
to ground from VDD.
! Note: systems using lithium batteries should clear the
VBC bit to 0 to prevent battery charging. The VBAK
circuitry includes an internal 1 KΩ series resistor as a
safety element. The trickle charger is UL Recognized.
Page 6 of 21
FM32278/276/274/272 - 5V 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 =
Address
18h
17h
16h
15h
14h
13h
12h
11h
10h
0Fh
0Eh
0Dh
0Ch
0Bh
0Ah
09h
00-08h
D7
D6
SNL
WDE
WTR
POR
D5
D4
D3
Serial Number Byte 7
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
Counter 2 LSB
Counter 1 MSB
Counter 1 LSB
RC
FC
WP1
WP0
WDT4
WDT3
LB
WR3
DO NOT USE
D2
D1
D0
CC
VBC
WDT2
WR2
C2P
WDT1
WR1
C1P
VTP
WDT0
WR0
Function
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
Watchdog Control
Watchdog Restart/Flags
RESERVED
Range
FFh
FFh
FFh
FFh
FFh
FFh
FFh
FFh
FFh
FFh
FFh
FFh
*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 batterybacked 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
Rev. 3.0
Feb. 2009
Hex Value
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x1F
Page 7 of 21
FM32278/276/274/272 - 5V I2C Companion
Register Description
Address Description
18h
Serial Number Byte 7
D7
D6
D5
D4
D3
D2
D1
D0
SN.63
SN.62
SN.61
SN.60
SN.59
SN.58
SN.57
SN.56
Upper byte of the serial number. Read/write when SNL=0, read-only when SNL=1. Nonvolatile.
17h
Serial Number Byte 6
D7
D6
D5
D4
D3
D2
D1
D0
SN.55
SN.54
SN.53
SN.52
SN.51
SN.50
SN.49
SN.48
Byte 6 of the serial number. Read/write when SNL=0, read-only when SNL=1. Nonvolatile.
16h
Serial Number Byte 5
D7
D6
D5
D4
D3
D2
D1
D0
SN.47
SN.46
SN.45
SN.44
SN.43
SN.42
SN.41
SN.40
Byte 5 of the serial number. Read/write when SNL=0, read-only when SNL=1. Nonvolatile.
15h
Serial Number Byte 4
D7
D6
D5
D4
D3
D2
D1
D0
SN.39
SN.38
SN.37
SN.36
SN.35
SN.34
SN.33
SN.32
Byte 4 of the serial number. Read/write when SNL=0, read-only when SNL=1. Nonvolatile.
14h
Serial Number Byte 3
D7
D6
D5
D4
D3
D2
D1
D0
SN.31
SN.30
SN.29
SN.28
SN.27
SN.26
SN.25
SN.24
Byte 3 of the serial number. Read/write when SNL=0, read-only when SNL=1. Nonvolatile.
13h
Serial Number Byte 2
D7
D6
D5
D4
D3
D2
D1
D0
SN.23
SN.22
SN.21
SN.20
SN.19
SN.18
SN.17
SN.16
Byte 2 of the serial number. Read/write when SNL=0, read-only when SNL=1. Nonvolatile.
12h
Serial Number Byte 1
D7
D6
D5
D4
D3
D2
D1
D0
SN.15
SN.14
SN.13
SN.12
SN.11
SN.10
SN.9
SN.8
Byte 1 of the serial number. Read/write when SNL=0, read-only when SNL=1. Nonvolatile.
11h
Serial Number Byte 0
D7
D6
D5
D4
D3
D2
D1
D0
SN.7
SN.6
SN.5
SN.4
SN.3
SN.2
SN.1
SN.0
LSB of the serial number. Read/write when SNL=0, read-only when SNL=1. Nonvolatile.
10h
Counter 2 MSB
D7
D6
D5
D4
D3
D2
D1
D0
C2.15
C2.14
C2.13
C2.12
C2.11
C2.10
C2.9
C2.8
Event Counter 2 MSB. Increments on overflows from Counter 2 LSB. Battery-backed, read/write.
0Fh
Counter 2 LSB
D7
D6
D5
D4
D3
D2
D1
D0
C2.7
C2.6
C2.5
C2.4
C2.3
C2.2
C2.1
C2.0
Event Counter 2 LSB. Increments on programmed edge event on CNT2 input or overflows from Counter 1 MSB
when CC=1. Battery-backed, read/write .
0Eh
Counter 1 MSB
D7
D6
D5
D4
D3
D2
D1
D0
C1.15
C1.14
C1.13
C1.12
C1.11
C1.10
C1.9
C1.8
Event Counter 1 MSB. Increments on overflows from Counter 1 LSB. Battery-backed, read/write.
0Dh
Counter 1 LSB
D7
D6
D5
D4
D3
D2
D1
D0
C1.7
C1.6
C1.5
C1.4
C1.3
C1.2
C1.1
C1.0
Event Counter 1 LSB. Increments on programmed edge event on CNT1 input. Battery-backed, read/write.
Rev. 3.0
Feb. 2009
Page 8 of 21
FM32278/276/274/272 - 5V I2C Companion
0Ch
RC
CC
C2P
C1P
0Bh
SNL
FC
WP1-0
Event Counter Control
D7
D6
D5
D4
D3
D2
D1
D0
-
-
-
-
RC
CC
C2P
C1P
Read Counter. Setting this bit to 1 takes a snapshot of the four counters bytes allowing the system to read the
values without missing count events. The RC bit will be automatically cleared.
Counter Cascade. When CC=0, the event counters operate independently according to the edge programmed by
C1P and C2P respectively. When CC=1, the counters are cascaded to create one 32-bit counter. The registers of
Counter 2 represent the most significant 16-bits of the counter and CNT1 is the controlling input. Bit C2P is
“don’t care” when CC=1. Battery-backed, read/write.
CNT2 detects falling edges when C2P = 0, rising edges when C2P = 1. C2P is “don’t care” when CC=1. The value
of Event Counter 2 may inadvertently increment if C2P is changed. Battery-backed, read/write.
CNT1 detects falling edges when C1P = 0, rising edges when C1P = 1. The value of Event Counter 1 may
inadvertently increment if C1P is changed. Battery-backed, read/write.
Companion Control
D7
D6
D5
D4
D3
D2
D1
D0
SNL
-
FC
WP1
WP0
VBC
-
VTP
Serial Number Lock. Setting to a 1 makes registers 11h to 18h and SNL permanently read-only. SNL cannot be
cleared once set to 1. Nonvolatile, read/write.
Fast Charge: Setting FC to ‘1’ (and VBC=1) causes a ~1 mA trickle charge current to be supplied on VBAK.
Clearing VBC to ‘0’ disables the charge current. Nonvolatile, read/write.
Write Protect. These bits control the write protection of the memory array. Nonvolatile, read/write.
Write protect addresses
None
Bottom 1/4
Bottom 1/2
Full array
VBC
WP1
0
0
1
1
WP0
0
1
0
1
VTP
VBAK Charger Control. Setting VBC to ‘1’ (and FC=0) causes a ~80 µA (1 mA if FC=1) trickle charge current to
be supplied on VBAK. Clearing VBC to ‘0’ disables the charge current. Nonvolatile, read/write.
VTP select. This bit controls the reset trip point for the low VDD reset function. Nonvolatile, read/write.
0Ah
Trip Voltage
3.9V
4.4V
Watchdog Control
WDE
WDT4-0
VTP
0
1
D7
D6
D5
D4
D3
D2
D1
D0
WDE
-
-
WDT4
WDT3
WDT2
WDT1
WDT0
Watchdog Enable. When WDE=1, a watchdog timer fault will cause the /RST signal to go active. When WDE = 0
the timer runs but has no effect on /RST, however the WTR flag will be set when a fault occurs. Note as the timer
is free-running, users should restart the timer using WR3-0 prior to setting WDE=1. This assures a full watchdog
timeout interval occurs. Nonvolatile, read/write.
Watchdog Timeout. Indicates the minimum watchdog timeout interval with 100 ms resolution. New watchdog
timeouts are loaded when the timer is restarted by writing the 1010b pattern to WR3-0. Nonvolatile, read/write.
Watchdog timeout
Invalid – default 100 ms
100 ms
200 ms
300 ms
.
.
.
2000 ms
2100 ms
2200 ms
.
.
.
2900 ms
3000 ms
Disable counter
Rev. 3.0
Feb. 2009
WDT4 WDT3 WDT2 WDT1 WDT0
0
0
0
0
0
0
0
0
0
1
0
0
0
1
0
0
0
0
1
1
1
1
1
0
0
0
1
1
1
0
0
1
0
1
0
1
1
1
1
1
1
1
1
1
0
1
1
1
0
1
Page 9 of 21
FM32278/276/274/272 - 5V I2C Companion
09h
WTR
POR
LB
WR3-0
00-08h
Rev. 3.0
Feb. 2009
Watchdog Restart & Flags
D7
D6
D5
D4
D3
D2
D1
D0
WTR
POR
LB
-
WR3
WR2
WR1
WR0
Watchdog Timer Reset Flag: When a watchdog timer fault occurs, the WTR bit will be set to 1. It must be cleared
by the user. Note that both WTR and POR could be set if both reset sources have occurred since the flags were
cleared by the user. Battery-backed. Read/Write (internally set, user can clear bit).
Power-on Reset Flag: When the /RST pin is activated by either VDD < VTP or a manual reset, the POR bit will be
set to 1. It must be cleared by the user. Note that both WTR and POR could be set if both reset sources have
occurred since the flags were cleared by the user. Battery-backed. Read/Write (internally set, user can clear bit).
Low Backup Flag: On power up, if the VBAK source is below the minimum voltage to operate the event counters,
this bit will be set to 1. The user should clear it to 0 when initializing the system. Battery-backed. Read/Write
(internally set, user can clear bit).
Watchdog Restart: Writing a pattern 1010b to WR3-0 restarts the watchdog timer. The upper nibble contents do
not affect this operation. Writing any pattern other than 1010b to WR3-0 has no effect on the timer. This allows
users to clear the WTR, POR, and LB flags without affecting the watchdog timer. Battery-backed, Write-only.
Reserved – DO NOT USE THIS ADDRESS SPACE
Page 10 of 21
FM32278/276/274/272 - 5V I2C Companion
By convention, any device that is sending data onto
the bus is the transmitter while the target device for
this data is the receiver. The device that is
controlling the bus is the master. The master is
responsible for generating the clock signal for all
operations. Any device on the bus that is being
controlled is a slave. The FM3227x is always a slave
device.
Two-wire Interface
The FM3227x employs an industry standard twowire bus that is familiar to many users. This product
is unique since it incorporates two logical devices in
one chip. Each logical device can be accessed
individually. Although monolithic, it appears to the
system software to be two separate products. One is
a memory device. It has a Slave Address (Slave ID =
1010b) that operates the same as a stand-alone
memory device. The second device is a real-time
clock and processor companion which have a unique
Slave Address (Slave ID = 1101b).
The bus protocol is controlled by transition states in
the SDA and SCL signals. There are four conditions:
Start, Stop, Data bit, and Acknowledge. The figure
below illustrates the signal conditions that specify
the four states. Detailed timing diagrams are shown
in the Electrical Specifications section.
SCL
7
SDA
Stop
(Master)
Start
(Master)
6
Data bits
(Transmitter)
0
Data bit Acknowledge
(Transmitter) (Receiver)
Figure 9. Data Transfer Protocol
Start Condition
A Start condition is indicated when the bus master
drives SDA from high to low while the SCL signal is
high. All read and write transactions begin with a
Start condition. An operation in progress can be
aborted by asserting a Start condition at any time.
Aborting an operation using the Start condition will
ready the FM3227x for a new operation.
If the power supply drops below the specified VTP
during operation, any 2-wire transaction in progress
will be aborted and the system must issue a Start
condition prior to performing another operation.
Stop Condition
A Stop condition is indicated when the bus master
drives SDA from low to high while the SCL signal is
high. All operations must end with a Stop condition.
If an operation is pending when a stop is asserted,
the operation will be aborted. The master must have
control of SDA (not a memory read) in order to
assert a Stop condition.
Data/Address Transfer
All data transfers (including addresses) take place
while the SCL signal is high. Except under the two
conditions described above, the SDA signal should
not change while SCL is high.
Rev. 3.0
Feb. 2009
Acknowledge
The Acknowledge (ACK) takes place after the 8th
data bit has been transferred in any transaction.
During this state the transmitter must release the
SDA bus to allow the receiver to drive it. The
receiver drives the SDA signal low to acknowledge
receipt of the byte. If the receiver does not drive
SDA low, the condition is a No-Acknowledge
(NACK) and the operation is aborted.
The receiver might NACK for two distinct reasons.
First is that a byte transfer fails. In this case, the
NACK ends the current operation so that the part can
be addressed again. This allows the last byte to be
recovered in the event of a communication error.
Second and most common, the receiver does not
send an ACK to deliberately terminate an operation.
For example, during a read operation, the FM3227x
will continue to place data onto the bus as long as the
receiver sends ACKs (and clocks). When a read
operation is complete and no more data is needed,
the receiver must NACK the last byte. If the receiver
ACKs the last byte, this will cause the FM3227x to
attempt to drive the bus on the next clock while the
master is sending a new command such as a Stop.
Page 11 of 21
FM32278/276/274/272 - 5V I2C Companion
Slave Address
The first byte that the FM3227x expects after a Start
condition is the slave address. As shown in figures
below, the slave address contains the Slave ID,
Device Select address, and a bit that specifies if the
transaction is a read or a write.
The FM3227x has two Slave Addresses (Slave IDs)
associated with two logical devices. To access the
memory device, bits 7-4 should be set to 1010b. The
other logical device within the FM3227x is the realtime clock and companion. To access this device,
bits 7-4 of the slave address should be set to 1101b.
A bus transaction with this slave address will not
affect the memory in any way. The figures below
illustrate the two Slave Addresses.
The Device Select bits allow multiple devices of the
same type to reside on the 2-wire bus. The device
select bits (bits 2-1) select one of four parts on a twowire bus. They must match the corresponding value
on the external address pins in order to select the
device. Bit 0 is the read/write bit. A “1” indicates a
read operation, and a “0” indicates a write operation.
Device
Select
Slave ID
1
7
0
1
0
X
A1
A0
R/W
6
5
4
3
2
1
0
Figure 10. Slave Address - Memory
Device
Select
Slave ID
1
7
1
0
1
X
A1
A0
R/W
6
5
4
3
2
1
0
Figure 11. Slave Address – Companion
Addressing Overview – Memory
After the FM3227x acknowledges the Slave
Address, the master can place the memory address
on the bus for a write operation. The address requires
two bytes. This is true for all members of the family.
Therefore the 4Kb and 16Kb configurations will be
addressed differently from stand alone serial
memories but the entire family will be upwardly
compatible with no software changes.
The first is the MSB (upper byte). For a given
density unused address bits are don’t cares, but
should be set to 0 to maintain upward compatibility.
Rev. 3.0
Feb. 2009
Following the MSB is the LSB (lower byte) which
contains the remaining eight address bits. The
address is latched internally. Each access causes the
latched address to be incremented automatically. The
current address is the value that is held in the latch,
either a newly written value or the address following
the last access. The current address will be held as
long as VDD > VTP or until a new value is written.
Accesses to the clock do not affect the current
memory address. Reads always use the current
address. A random read address can be loaded by
beginning a write operation as explained below.
After transmission of each data byte, just prior to the
Acknowledge, the FM3227x increments the internal
address. This allows the next sequential byte to be
accessed with no additional addressing externally.
After the last address is reached, the address latch
will roll over to 0000h. There is no limit to the
number of bytes that can be accessed with a single
read or write operation.
Addressing Overview – Companion
The Processor Companion operates in a similar
manner to the memory, except that it uses only one
byte of address. Addresses 00h to 18h correspond to
special function registers. Attempting to load
addresses above 18h is an illegal condition; the
FM3227x will return a NACK and abort the 2-wire
transaction.
Data Transfer
After the address information has been transmitted,
data transfer between the bus master and the
FM3227x begins. For a read, the FM3227x will
place 8 data bits on the bus then wait for an ACK
from the master. If the ACK occurs, the FM3127x
will transfer the next byte. If the ACK is not sent, the
FM3227x will end the read operation. For a write
operation, the FM3227x will accept 8 data bits from
the master then send an Acknowledge. All data
transfer occurs MSB (most significant bit) first.
Memory Write Operation
All memory writes begin with a Slave Address, then
a memory address. The bus master indicates a write
operation by setting the slave address LSB to a 0.
After addressing, the bus master sends each byte of
data to the memory and the memory generates an
Acknowledge condition. Any number of sequential
bytes may be written. If the end of the address range
is reached internally, the address counter will wrap
to 0000h. Internally, the actual memory write occurs
after the 8th data bit is transferred. It will be complete
before the Acknowledge is sent. Therefore, if the
Page 12 of 21
FM32278/276/274/272 - 5V I2C Companion
user desires to abort a write without altering the
memory contents, this should be done using a Start
or Stop condition prior to the 8th data bit. The figures
By Master
Stop
Address & Data
Start
S
below illustrate a single- and multiple-writes to
memory.
Slave Address
0 A
Address MSB
A
Address LSB
A
Data Byte
A
P
By FM3227x
Acknowledge
Figure 12. Single Byte Memory Write
Start
S
By FM3227x
Stop
Address & Data
By Master
Slave Address
0
A
Address MSB
A
Address LSB
A
Data Byte
A
Data Byte
A
P
Acknowledge
Figure 13. Multiple Byte Memory Write
Memory Read Operation
There are two types of memory read operations. They
are current address read and selective address read. In
a current address read, the FM3227x uses the internal
address latch to supply the address. In a selective
read, the user performs a procedure to first set the
address to a specific value.
Current Address & Sequential Read
As mentioned above the FM3227x uses an internal
latch to supply the address for a read operation. A
current address read uses the existing value in the
address latch as a starting place for the read
operation. The system reads from the address
immediately following that of the last operation.
To perform a current address read, the bus master
supplies a slave address with the LSB set to 1. This
indicates that a read operation is requested. After
receiving the complete device address, the FM3227x
will begin shifting data out from the current address
on the next clock. The current address is the value
held in the internal address latch.
Beginning with the current address, the bus master
can read any number of bytes. Thus, a sequential read
is simply a current address read with multiple byte
transfers. After each byte the internal address counter
will be incremented.
Rev. 3.0
Feb. 2009
Each time the bus master acknowledges a byte,
this indicates that the FM3227x should read out
the next sequential byte.
There are four ways to terminate a read operation.
Failing to properly terminate the read will most likely
create a bus contention as the FM3227x attempts to
read out additional data onto the bus. The four valid
methods follow.
1.
2.
3.
4.
The bus master issues a NACK in the 9th clock
cycle and a Stop in the 10th clock cycle. This is
illustrated in the diagrams below and is
preferred.
The bus master issues a NACK in the 9th clock
cycle and a Start in the 10th.
The bus master issues a Stop in the 9th clock
cycle.
The bus master issues a Start in the 9th clock
cycle.
If the internal address reaches the top of memory, it
will wrap around to 0000h on the next read cycle.
The figures below show the proper operation for
current address reads.
Selective (Random) Read
There is a simple technique that allows a user to
select a random address location as the starting point
for a read operation. This involves using the first
Page 13 of 21
FM32278/276/274/272 - 5V I2C Companion
master supplies a Slave Address with the LSB set to
1. This indicates that a read operation is requested.
After receiving the complete Slave Address, the
FM3227x will begin shifting data out from the
current register address on the next clock. Autoincrement operates for the special function registers
as with the memory address. A current address read
for the registers look exactly like the memory except
that the device ID is different.
three bytes of a write operation to set the internal
address followed by subsequent read operations.
To perform a selective read, the bus master sends out
the slave address with the LSB set to 0. This specifies
a write operation. According to the write protocol,
the bus master then sends the address bytes that are
loaded into the internal address latch. After the
FM3127x acknowledges the address, the bus master
issues a Start condition. This simultaneously aborts
the write operation and allows the read command to
be issued with the slave address LSB set to a 1. The
operation is now a read from the current address.
Read operations are illustrated below.
The FM3227x contains two separate address
registers, one for the memory address and the other
for the register address. This allows the contents of
one address register to be modified without affecting
the current address of the other register. For example,
this would allow an interrupted read to the memory
while still providing fast access to a companion
register. A subsequent memory read will then
continue from the memory address where it
previously left off, without requiring the load of a
new memory address. However, a write sequence
always requires an address to be supplied.
Companion Write Operation
All Companion writes operate in a similar manner to
memory writes. The distinction is that a different
device ID is used and only one byte address is needed
instead of two. Figure 16 illustrates a single byte
write to this device.
Companion Read Operation
As with writes, a read operation begins with the
Slave Address. To perform a register read, the bus
Start
By Master
No
Acknowledge
Address
Stop
S
Slave Address
By FM3227x
1 A
Acknowledge
Data Byte
1
P
Data
Figure 14. Current Address Memory Read
By Master
Start
No
Acknowledge
Acknowledge
Stop
S
By FM3227x
Address
Slave Address 1 A
Acknowledge
Data Byte
A
Data Byte
1 P
Data
Figure 15. Sequential Memory Read
Rev. 3.0
Feb. 2009
Page 14 of 21
FM32278/276/274/272 - 5V I2C Companion
Start
Address
By Master
Start
No
Acknowledge
Address
Stop
S
Slave Address 0 A
Address MSB
A
By FM3227x
Address LSB
A S
Slave Address 1 A
Data Byte
1 P
Data
Acknowledge
Figure 16. Selective (Random) Memory Read
By Master
Address & Data
Start
S
Slave Address
0 A 0 0 0
Address
By FM3227x
Stop
A
A
Data Byte
P
Acknowledge
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 FM3227x Family
The FM3227x 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 #
1st Address Byte
FM32278
FM32276
FM32274
FM32272
Rev. 3.0
Feb. 2009
x
x
x
x
A14
x
x
x
A13
x
x
x
A12
A12
x
x
A11
A11
x
x
2nd Address Byte
A10
A10
A10
x
A9
A9
A9
x
A8
A8
A8
A8
A7
A7
A7
A7
A6
A6
A6
A6
A5
A5
A5
A5
A4
A4
A4
A4
A3
A3
A3
A3
A2
A2
A2
A2
A1
A1
A1
A1
A0
A0
A0
A0
Page 15 of 21
FM32278/276/274/272 - 5V I2C Companion
Electrical Specifications
Absolute Maximum Ratings
Symbol
Description
VDD
Power Supply Voltage with respect to VSS
VIN
Voltage on any signal pin with respect to VSS
VBAK
TSTG
TLEAD
VESD
Ratings
-1.0V to +7.0V
-1.0V to +7.0V * and
VIN ≤ VDD+1.0V **
-1.0V to +4.5V
-55°C to + 125°C
300° C
Backup Supply Voltage
Storage Temperature
Lead Temperature (Soldering, 10 seconds)
Electrostatic Discharge Voltage
- Human Body Model (JEDEC Std JESD22-A114-B)
- Charged Device Model (JEDEC Std JESD22-C101-A)
Package Moisture Sensitivity Level
3kV
1kV
MSL-1
* PFI input voltage must not exceed 4.5V.
** The “VIN < VDD+1.0V” restriction does not apply to the SCL and SDA inputs which do not employ a diode to VDD.
Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only,
and the functional operation of the device at these or any other conditions above those listed in the operational section of this
specification is not implied. Exposure to absolute maximum ratings conditions for extended periods may affect device reliability.
DC Operating Conditions (TA = -40° C to + 85° C, VDD = 4.0V to 5.5V unless otherwise specified)
Symbol
Parameter
Min
Typ
Max
VDD
Main Power Supply
4.0
5.5
IDD
VDD Supply Current
@ SCL = 100 kHz
500
@ SCL = 400 kHz
900
@ SCL = 1 MHz
1500
ISB
Standby Current
150
VBAK
IBAK
IBAKTC
VTP1
VTP2
VRST
ILI
ILO
VIL
VIH
VOL
VOH
RRST
Rev. 3.0
Feb. 2009
Backup Supply Voltage
Backup Supply Current
Trickle Charge Current with VBAK=0V
Fast Charge Off (FC = 0)
Fast Charge On (FC = 1)
VDD Trip Point Voltage, VTP = 0
VDD Trip Point Voltage, VTP = 1
VDD for valid /RST @ IOL = 80 µA at VOL
VBAK > VBAK min
VBAK < VBAK min
Input Leakage Current
Output Leakage Current
Input Low Voltage
All inputs except those listed below
CNT1-2 battery backed (VDD < 2.5V)
CNT1-2 (VDD > 2.5V)
Input High Voltage
All inputs except those listed below
PFI (comparator input)
CNT1-2 battery backed (VDD < 2.5V)
CNT1-2 VDD > 2.5V
Output Low Voltage (IOL = 3 mA)
Output High Voltage (IOH = -2 mA)
Pull-up Resistance for /RST Inactive
Units
V
µA
µA
µA
µA
2.0
3.0
3.75
1
V
µA
50
200
3.80
4.25
3.9
4.4
120
2500
4.00
4.50
µA
µA
V
V
±1
±1
V
V
µA
µA
-0.3
-0.3
-0.3
0.3 VDD
0.5
0.8
V
V
V
0.7 VDD
VBAK – 0.5
0.7 VDD
2.4
50
VDD + 0.3
3.75
VBAK + 0.3
VDD + 0.3
0.4
400
Continued
V
V
V
V
V
V
KΩ
»
0
1.6
Notes
7
1
2
9
4
10
5
5
6
3
3
8
Page 16 of 21
FM32278/276/274/272 - 5V I2C Companion
DC Operating Conditions, continued (TA = -40° C to + 85° C, VDD = 4.0V to 5.5V unless otherwise specified)
Symbol Parameter
Min
Typ
Max
Units
RIN
Input Resistance (pulldown)
20
A1-A0 for VIN = VIL max
KΩ
1
A1-A0 for VIN = VIH min
MΩ
VPFI
Power Fail Input Reference Voltage
1.175
1.20
1.225
V
VHYS
Power Fail Input (PFI) Hysteresis (Rising)
100
mV
Notes
Notes
1. SCL toggling between VDD-0.3V and VSS, other inputs VSS or VDD-0.3V.
2. All inputs at VSS or VDD, static. Stop command issued.
3. VIN or VOUT = VSS to VDD. Does not apply to A0, A1, or /RST pins.
4. VBAK = 3.0V, VDD < 2.4V, oscillator running, CNT1-2 at VBAK.
5. /RST is asserted low when VDD < VTP.
6. The minimum VDD to guarantee the level of /RST remains a valid VOL level.
7. Full complete operation. Supervisory circuits operate to lower voltages as specified.
8. Includes /RST input detection of external reset condition to trigger driving of /RST signal by FM3227x.
9. The VBAK trickle charger automatically regulates the maximum voltage on this pin for capacitor backup applications.
10. VBAK will source current when trickle charge is enabled (VBC bit=1), VDD > VBAK, and VBAK < VBAK max.
AC Parameters (TA = -40° C to + 85° C, VDD = 4.0V to 5.5V, CL = 100 pF unless otherwise specified)
Symbol Parameter
Min Max Min Max Min Max
fSCL
SCL Clock Frequency
0
100
0
400
0
1000
tLOW
Clock Low Period
4.7
1.3
0.6
tHIGH
Clock High Period
4.0
0.6
0.4
tAA
SCL Low to SDA Data Out Valid
3
0.9
0.55
tBUF
tHD:STA
tSU:STA
tHD:DAT
tSU:DAT
tR
tF
tSU:STO
tDH
tSP
Bus Free Before New Transmission
Start Condition Hold Time
Start Condition Setup for Repeated
Start
Data In Hold Time
Data In Setup Time
Input Rise Time
Input Fall Time
Stop Condition Setup Time
Data Output Hold (from SCL @ VIL)
Noise Suppression Time Constant
on SCL, SDA
Units
kHz
µs
µs
µs
4.7
4.0
4.7
1.3
0.6
0.6
0.5
0.25
0.25
µs
µs
µs
0
250
0
100
0
100
ns
ns
ns
ns
µs
ns
ns
1000
300
4.0
0
300
300
0.6
0
300
100
0.25
0
50
50
50
Notes
1
1
All SCL specifications as well as start and stop conditions apply to both read and write operations.
Capacitance (TA = 25° C, f=1.0 MHz, VDD = 5.0V)
Symbol
Parameter
CIO
Input/Output Capacitance
Typ
-
Max
8
Units
pF
Notes
1
Notes
1
This parameter is characterized but not tested.
Data Retention (VDD = 4.0V to 5.5V)
Symbol
Parameter
TDR
Data Retention
@ +75°C
@ +80°C
@ +85°C
Rev. 3.0
Feb. 2009
Min
Units
45
20
10
Years
Years
Years
Notes
Page 17 of 21
FM32278/276/274/272 - 5V I2C Companion
Supervisor Timing (TA = -40° C to + 85° C, VDD = 4.0V to 5.5V)
Symbol
Parameter
tRPU
/RST Active (low) after VDD>VTP
tRNR
VDD < VTP noise immunity
tVR
VDD Rise Time
tVF
VDD Fall Time
tWDP
Pulse Width of /RST for Watchdog Reset
tWDOG
Timeout of Watchdog
fCNT
Frequency of Event Counters
Min
100
10
50
100
100
tDOG
0
Max
200
25
200
2*tDOG
10
Units
ms
µs
µs/V
µs/V
ms
ms
MHz
Notes
1
1,2
1,2
3
Notes
1
This parameter is characterized but not tested.
2
Slope measured at any point on VDD waveform.
3
tDOG is the programmed time in register 0Ah, VDD > VTP and tRPU satisfied.
/RST Timing
VDD
VTP
VRST
t RNR
t RPU
RST
Rev. 3.0
Feb. 2009
Page 18 of 21
FM32278/276/274/272 - 5V I2C Companion
AC Test Conditions
Equivalent AC Load Circuit
Input Pulse Levels
Input rise and fall times
Input and output timing levels
5.5V
0.1 VDD to 0.9 VDD
10 ns
0.5 VDD
1700 Ω
Diagram Notes
All start and stop timing parameters apply to both read and write
cycles. Clock specifications are identical for read and write cycles.
Write timing parameters apply to slave address, word address, and
write data bits. Functional relationships are illustrated in the relevant
data sheet sections. These diagrams illustrate the timing parameters
only.
Output
100 pF
Read Bus Timing
tR
`
tF
t HIGH
t SP
t LOW
t SP
SCL
t SU:STA
1/fSCL
tBUF
t HD:DAT
t SU:DAT
SDA
Start
t DH
tAA
Stop Start
Acknowledge
Write Bus Timing
tHD:DAT
SCL
tHD:STA
tSU:STO
tSU:DAT
tAA
SDA
Start
Rev. 3.0
Feb. 2009
Stop Start
Acknowledge
Page 19 of 21
FM32278/276/274/272 - 5V I2C Companion
Mechanical Drawing
14-pin SOIC (JEDEC Standard MS-012, Variation AB)
Recommended PCB Footprint
...
7.70
3.70
6.00 ±0.20
3.90 ±0.13
...
2.00
0.65
1.27
Pin 1
8.64 ±0.10
1.27
1.35
1.75
0.10
0.25
0.33
0.51
0.25
0.50
0.10 mm
0.19
0.25
45 °
0°- 8°
0.40
1.27
Refer to JEDEC MS-012 for complete dimensions and notes.
All dimensions in millimeters.
SOIC Package Marking Scheme
XXXXXXX-P
LLLLLLL
RIC YYWW
Legend:
XXXX= part number, P= package type (-S, -G)
LLLLLLL= lot code
RIC=Ramtron Int’l Corp, YY=year, WW=work week
Example: FM32278, “Green”/RoHS SOIC package,
Year 2007, Work Week 36
FM32278-G
A70023G
RIC 0736
Rev. 3.0
Feb. 2009
Page 20 of 21
FM32278/276/274/272 - 5V I2C Companion
Revision History
Revision
2.0
3.0
Rev. 3.0
Feb. 2009
Date
12/14/07
2/9/2009
Summary
Initial release.
Changed status to Production. Added tape and reel ordering information.
Expanded data retention ratings. Added UL Recognition of trickle charger.
Page 21 of 21