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FM24CL04(FM24CL04).pdf
FM24CL04
4Kb FRAM Serial Memory
Features
4K bit Ferroelectric Nonvolatile RAM
• Organized as 512 x 8 bits
• Unlimited Read/Writes
•
45 Year Data Retention
• NoDelay™ Writes
• Advanced High-Reliability Ferroelectric Process
Fast Two-wire Serial Interface
• Up to 1 MHz maximum bus frequency
• Direct hardware replacement for EEPROM
Description
The FM24CL04 is a 4-kilobit nonvolatile memory
employing an advanced ferroelectric process. A
ferroelectric random access memory or FRAM is
nonvolatile and performs reads and writes like a
RAM. It provides reliable data retention for 45 years
while eliminating the complexities, overhead, and
system level reliability problems caused by EEPROM
and other nonvolatile memories.
Unlike serial EEPROMs, the FM24CL04 performs
write operations at bus speed. No write delays are
incurred. Data is written to the memory array in the
cycle after it has been successfully transferred to the
device. The next bus cycle may commence
immediately.
These capabilities make the FM24CL04 ideal for
nonvolatile memory applications requiring frequent
or rapid writes. Examples range from data collection
where the number of write cycles may be critical, to
demanding industrial controls where the long write
time of EEPROM can cause data
loss. The
combination of features allows more frequent data
writing with less overhead for the system.
The FM24CL04 provides substantial benefits to users
of serial EEPROM, yet these benefits are available in
a hardware drop-in replacement. The FM24CL04 is
available in an industry standard 8-pin package using
a
are
guaranteed over an industrial temperature range of
-40°C to +85°C.
two-wire protocol. The
specifications
2.7V to 3.65V operation
75 µA Active Current (100 kHz) @ 3V
1 µA Standby Current
Low Power Operation
•
•
•
Industry Standard Configuration
•
•
•
Industrial Temperature -40° C to +85° C
8-pin SOIC (-S)
“Green” 8-pin SOIC (-G)
Pin Configuration
NC
A1
A2
VSS
1
2
3
4
8
7
6
5
VDD
WP
SCL
SDA
Pin Names
A1-A2
SDA
SCL
WP
VSS
VDD
Function
Device Select Address 1 and 2
Serial Data/Address
Serial Clock
Write Protect
Ground
Supply Voltage 3V
Ordering Information
FM24CL04-S
FM24CL04-G
8-pin SOIC
“Green” 8-pin SOIC
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
March 2005
Ramtron International Corporation
1850 Ramtron Drive, Colorado Springs, CO 80921
(800) 545-FRAM, (719) 481-7000
www.ramtron.com
Page 1 of 11
FM24CL04
Counter
Address
Latch
128 x 32
FRAM Array
`
Serial to Parallel
Converter
Control Logic
SDA
SCL
WP
A1
A2
8
Data Latch
Figure 1. Block Diagram
Pin Description
Address 1-2: The address pins set the device select address. The device address value
in the 2-wire slave address must match the setting of these two pins. These pins are
internally pulled down.
Serial Data/Address: This is a bi-directional pin used to shift serial data and addresses
for the two-wire interface. It employs an open-drain output 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 input for the two-wire interface. Data is clocked out of
the device on the SCL falling edge, and clocked in on the SCL rising edge. The SCL
input also incorporates a Schmitt trigger input for improved noise immunity.
Pin Description
Pin Name
A1-A2
I/O
Input
SDA
I/O
SCL
Input
WP
NC
VDD
VSS
Rev. 3.0
March 2005
Input Write Protect: When WP is high the entire array is write protected. When WP is low,
all addresses may be written. This pin is internally pulled down.
No connect
Supply Voltage
-
Supply
Supply Ground
Page 2 of 11
FM24CL04
two-wire bus
industry standard
Two-wire Interface
The FM24CL04 employs a bi-directional two-wire
bus protocol using few pins and little board space.
Figure 2 illustrates a typical system configuration
using the FM24CL04 in a microcontroller-based
system. The
is
familiar to many users but is described in this section.
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 FM24CL04 is always a slave device.
The bus protocol is controlled by transition states in
the SDA and SCL signals. There are four conditions:
Start, Stop, Data bit, and Acknowledge. Figure 3
illustrates the signal conditions that specify the four
states. Detailed timing diagrams are shown in the
electrical specifications.
Microcontroller
VDD
Rmin = 1.1 KΩ
Rmax = tR/Cbus
SDA
SCL
SDA
SCL
FM24CL04
A1 A2
FM24CL64
A0 A1 A2
Figure 2. Typical System Configuration
Overview
The FM24CL04 is a serial FRAM memory. The
memory array is logically organized as 512 x 8 and is
accessed using an
two-wire
interface. Functional operation of the FRAM is
similar to serial EEPROMs. The major difference
between the FM24CL04 and a serial EEPROM with
the same pinout relates
its superior write
performance.
industry standard
to
functions of
Memory Architecture
When accessing the FM24CL04, the user addresses
512 locations each with 8 data bits. These data bits
are shifted serially. The 512 addresses are accessed
using the two-wire protocol, which includes a slave
address (to distinguish other devices), a page address,
and a word address. The word address consists of 8-
bits that specify one of 256 addresses. The page
address is 1-bit and so there are 2 pages each of 256
locations. The complete address of 9-bits specifies
each byte address uniquely.
Most
the FM24CL04 either are
controlled by the two-wire interface or are handled
automatically by on-board circuitry. The memory is
read or written at the speed of the two-wire bus.
Unlike an EEPROM, it is not necessary to poll the
device for a ready condition since writes occur at bus
speed. That is, by the time a new bus transaction can
be shifted into the part, a write operation will be
complete. This is explained in more detail in the
interface section below.
Users can expect several obvious system benefits
from the FM24CL04 due to its fast write cycle and
high endurance as compared with EEPROM.
However there are less obvious benefits as well. For
example in a high noise environment, the fast-write
operation is less susceptible to corruption than an
EEPROM since it is completed quickly. By contrast
an EEPROM requiring milliseconds to write is
vulnerable to noise during much of the cycle.
Note
the FM24CL04 contains no power
management circuits other than a simple internal
power-on reset. It is the user’s responsibility to ensure
that VDD is within data sheet tolerances to prevent
incorrect operation.
that
Rev. 3.0
March 2005
Page 3 of 11
FM24CL04
Figure 3. Data Transfer Protocol
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.
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
FM24CL04 for a new operation.
If during operation the power supply drops below the
specified VDD minimum, the system should issue a
Start condition prior to performing another operation.
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.
Acknowledge
The Acknowledge takes place after the 8th data bit has
been transferred in any transaction. During this state
the transmitter should 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 and the operation is aborted.
The receiver could fail to acknowledge for two distinct
reasons. First, if a byte transfer fails, the No-
Acknowledge ends the current operation so that the
device 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
Rev. 3.0
March 2005
the
last byte.
If
the
the
the data
is needed,
acknowledge
to deliberately end an
operation. For example, during a read operation, the
FM24CL04 will continue to place data onto the bus
as long as the receiver sends acknowledges (and
clocks). When a read operation is complete and no
receiver must not
more data
acknowledge
receiver
acknowledges the last byte, this will cause the
FM24CL04 to attempt to drive the bus on the next
clock while the master is sending a new command
such as a Stop command.
Slave Address
The first byte that the FM24CL04 expects after a
start condition is the slave address. As shown in
Figure 4, the slave address contains the device type,
the device select, the page of memory to be
accessed, and a bit that specifies if the transaction is
a read or a write.
Bits 7-4 are the device type and should be set to
1010b for the FM24CL04. The device type allows
other types of functions to reside on the 2-wire bus
within an identical address range. Bits 3-2 are the
device address. If bit 3 matches the A2 pin and bit 2
matches the A1 pin the device will be selected. Bit 1
is the page select. It specifies the 256-byte block of
memory that is targeted for the current operation. Bit
0 is the read/write bit. A 0 indicates a write
operation.
Word Address
After the FM24CL04 (as receiver) acknowledges the
slave ID, the master will place the word address on
the bus for a write operation. The word address is
the lower 8-bits of the address to be combined with
the 1-bit page select to specify exactly the byte to be
written. The complete 9-bit address is latched
internally.
Page 4 of 11
FM24CL04
Figure 4. Slave Address
No word address occurs for a read operation. Reads
always use the lower 8-bits that are held internally in
the address latch and the 9th address bit is part of the
slave address. Reads always begin at the address
following the previous access. A random read address
can be loaded by doing a write operation as explained
below.
After transmission of each data byte, just prior to the
acknowledge, the FM24CL04 increments the internal
address latch. This allows the next sequential byte to
be accessed with no additional addressing. After the
last address (1FFh) is reached, the address latch will
roll over to 000h. There is no limit to the number of
bytes that can be accessed with a single read or write
operation.
Data Transfer
After all address information has been transmitted,
data
the
FM24CL04 can begin. For a read operation the
FM24CL04 will place 8 data bits on the bus then wait
for an acknowledge. If the acknowledge occurs, the
next sequential byte will be transferred. If the
acknowledge is not sent, the read operation is
concluded. For a write operation, the FM24CL04 will
accept 8 data bits from the master then send an
acknowledge. All data transfer occurs MSB (most
significant bit) first.
the bus master and
transfer between
Memory Operation
The FM24CL04 is designed to operate in a manner
very similar to other 2-wire interface memory
products. The major differences result from the
higher performance write capability of FRAM
technology. These improvements result in some
differences between the FM24CL04 and a similar
configuration EEPROM during writes. The complete
operation for both writes and reads is explained
below.
Write Operation
All writes begin with a slave address then a word
address. The bus master indicates a write operation
by setting the LSB of the Slave address 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
from 1FFh to 000h.
Unlike other nonvolatile memory technologies, there
is no write delay with FRAM. The entire memory
cycle occurs in less time than a single bus clock.
Therefore any operation including read or write can
occur immediately following a write. Acknowledge
polling, a
to
determine if a write is complete is unnecessary and
will always return a done condition.
An actual memory array write occurs after the 8th
data bit is transferred. It will be complete before the
acknowledge is sent. Therefore if the 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 FM24CL04 needs no
page buffering.
Pulling write protect high will disable writes to the
entire array. The FM24CL04 will not acknowledge
data bytes that are written when write protect is
asserted. In addition, the address counter will not
increment if writes are attempted. Pulling WP low
(VSS) will deactivate this feature.
Figure 5 below illustrates both a single- and
multiple- byte write.
technique used with EEPROMs
Rev. 3.0
March 2005
Page 5 of 11
FM24CL04
By Master
Start
Address & Data
Stop
S
Slave Address
0
A
Word Address
A
Data Byte
A P
By FM24CL04
By Master
Start
Acknowledge
Figure 5. Byte Write
Address & Data
Stop
S
Slave Address
0
A
Word Address
A
Data Byte
A
Data Byte
A P
By FM24CL04
Acknowledge
Figure 6. Multiple Byte Write
Read Operation
There are two basic types of read operations. They are
current address read and selective address read. In a
current address read, the FM24CL04 uses the internal
address latch to supply the lower 8 address bits. In a
selective read, the user performs a procedure to set
these lower address bits to a specific value.
Current Address & Sequential Read
The FM24CL04 uses an internal latch to supply the
lower 8 address bits for a read operation. A current
address read uses the existing value in the address
latch as a starting place for the read operation. This is
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. The page
select bit in the slave address specifies the block of
memory that is used for the read operation. After the
acknowledge, the FM24CL04 will begin shifting out
data from the current address. The current address is
the bit from the slave address combined with the 8 bits
that were 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. Each time the bus master
acknowledges a byte,
the
FM24CL04 should read out the next sequential byte.
There are four ways to properly terminate a read
operation. Failing to properly terminate the read will
most likely create a bus contention as the FM24CL04
indicates
that
this
attempts to read out additional data onto the bus. The
four valid methods are as follows.
1. The bus master issues a no-acknowledge in the
9th clock cycle and a stop in the 10th clock cycle.
This is illustrated in the diagrams below. This is
the preferred method.
2. The bus master issues a no-acknowledge in the
9th clock cycle and a start in the 10th.
3. The bus master issues a stop in the 9th clock
cycle. Bus contention may result.
4. The bus master issues a start in the 9th clock
cycle. Bus contention may result.
If the internal address reaches 1FFh it will wrap
around to 000h on the next read cycle. Figures 7 and
8 show the proper operation for current address reads.
Selective (Random) Read
A simple technique allows a user to select a random
address location as the starting point for a read
operation. This involves using the first two bytes of a
write operation to set the internal address byte
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 word address byte that is
loaded into the internal address latch. After the
FM24CL04 acknowledges the word 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 current address read.
See Figure 9.
Rev. 3.0
March 2005
Page 6 of 11
FM24CL04
Figure 7. Current Address Read
Figure 8. Sequential Read
Figure 9. Selective (Random) Read
Rev. 3.0
March 2005
Page 7 of 11
Electrical Specifications
FM24CL04
Absolute Maximum Ratings
Symbol
VDD
VIN
TSTG
TLEAD
VESD
Description
Ratings
Power Supply Voltage with respect to VSS
Voltage on any signal pin with respect to VSS
Storage Temperature
Lead Temperature (Soldering, 10 seconds)
Electrostatic Discharge Voltage
- Human Body Model (JEDEC Std JESD22-A114-B)
- Machine Model (JEDEC Std JESD22-A115-A)
Package Moisture Sensitivity Level
-1.0V to +5.0V
-1.0V to +5.0V
and VIN < VDD+1.0V *
-55°C to + 125°C
300° C
3kV
300V
MSL-1
* Exception: The “VIN < VDD+1.0V” restriction does not apply to the SCL and SDA inputs.
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 = 2.7V to 3.65V unless otherwise specified)
Symbol
VDD
IDD
ISB
ILI
ILO
VIH
VIL
VOL
RIN
Parameter
Main Power Supply
VDD Supply Current
@ SCL = 100 kHz
@ SCL = 400 kHz
@ SCL = 1 MHz
Standby Current
Input Leakage Current
Output Leakage Current
Input High Voltage
Input Low Voltage
Output Low Voltage
@ IOL = 3.0 mA
Input Resistance (WP, A2, A1)
For VIN = VIL (max)
For VIN = VIH (min)
Input Hysteresis
Typ
Min
2.7
0.7 VDD
-0.3
50
1
Max
3.65
75
150
300
1
±1
±1
VDD + 0.5
0.3 VDD
0.4
Units
Notes
V
µA
µA
µA
µA
µA
µA
V
V
V
KΩ
MΩ
V
1
2
3
3
5
4
VHYS
Notes
1. SCL toggling between VDD-0.3V and VSS, other inputs VSS or VDD-0.3V
2. SCL = SDA = VDD. All inputs VSS or VDD. Stop command issued.
3. VIN or VOUT = VSS to VDD. Does not apply to WP, A1, A2 pins.
4. This parameter is periodically sampled and not 100% tested.
0.05 VDD
Rev. 3.0
March 2005
Page 8 of 11
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