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PRELIMINARY DATA

October 1999

This is preliminary information on a new product now in development or undergoing evaluation. Details are subject to change without notice.

M14256
M14128

Memory Card IC

256/128 Kbit Serial I²C Bus EEPROM

Compatible with I

C Extended Addressing

Two Wire I

C Serial Interface

Supports 400 kHz Protocol

Single Supply Voltage (2.5 V to 5.5 V)

Hardware Write Control

BYTE and PAGE WRITE (up to 64 Bytes)

BYTE, RANDOM and SEQUENTIAL READ
Modes

Self-Timed Programming Cycle

Automatic Address Incrementing

Enhanced ESD/Latch-Up Behaviour

100,000 Erase/Write Cycles (minimum)

40 Year Data Retention (minimum)

5 ms Programming Time (typical)

DESCRIPTION
Each device is an electrically erasable program-
mable memory (EEPROM) fabricated with STMi-
croelectronics's High Endurance, Double
Polysilicon, CMOS technology. This guarantees
an endurance typically well above 100,000 Erase/
Write cycles, with a data retention of 40 years. The
memory operates with a power supply as low as
2.5 V.
The M14256 and M14128 are available in micro-
module form only. For availability of the M14256 or

Micromodule (D22)

Figure 1. Logic Diagram

AI02217

SDA

VCC

M14xxx

SCL

GND

Table 1. Signal Names

SDA

Serial Data/Address Input/
Output

SCL Serial

Clock

Write Control

Supply Voltage

GND Ground

M14256, M14128

2/12

M14128 in wafer form, please contact your ST
sales office.
Each memory device is compatible with the I

extended memory standard. This is a two wire se-
rial interface that uses a bi-directional data bus
and serial clock. The memory device carries a
built-in 7-bit unique Device Type Identifier code
(1010000) in accordance with the I

C bus defini-

tion. Only one memory device can be attached to
each I

C bus.

The memory device behaves as a slave device in
the I

C protocol, with all memory operations syn-

chronized by the serial clock. Read and write op-
erations are initiated by a START condition,
generated by the bus master. The START condi-
tion is followed by the Device Select Code which is
composed of a stream of 7 bits (1010000), plus
one read/write bit (R/W) and is terminated by an
acknowledge bit.

When writing data to the memory, the memory de-
vice inserts an acknowledge bit during the 9

bit

time, following the bus master's 8-bit transmission.
When data is read by the bus master, the bus
master acknowledges the receipt of the data byte
in the same way. Data transfers are terminated by
a STOP condition after an Ack for WRITE, and af-
ter a NoACK for READ.
Power On Reset: V

Lock-Out Write Protect

In order to prevent data corruption and inadvertent
write operations during power up, a Power On Re-
set (POR) circuit is included. The internal reset is
held active until the V

voltage has reached the

POR threshold value, and all operations are dis-
abled the device will not respond to any com-
mand. In the same way, when V

drops from the

operating voltage, below the POR threshold value,
all operations are disabled and the device will not
respond to any command. A stable and valid V

must be applied before applying any logic signal.

SIGNAL DESCRIPTION

Serial Clock (SCL)
The SCL input pin is used to synchronize all data
in and out of the memory. A pull up resistor can be
connected from the SCL line to V

. (Figure 3 in-

dicates how the value of the pull-up resistor can be
calculated).
Serial Data (SDA)
The SDA pin is bi-directional, and is used to trans-
fer data in or out of the memory. It is an open drain
output that may be wire-OR'ed with other open
drain or open collector signals on the bus. A pull
up resistor must be connected from the SDA bus
to V

. (Figure 3 indicates how the value of the

pull-up resistor can be calculated).

Figure 2. D22 Contact Connections

AI02204

VCC

GND

SCL

SDA

Table 2. Absolute Maximum Ratings

Note: 1. Except for the rating "Operating Temperature Range", stresses above those listed in the Table "Absolute Maximum Ratings" may

cause permanent damage to the device. These are stress ratings only, and operation of the device at these or any other conditions
above those indicated in the Operating sections of this specification is not implied. Exposure to Absolute Maximum Rating condi-
tions for extended periods may affect device reliability. Refer also to the ST SURE Program and other relevant quality documents.

2. MIL-STD-883C, 3015.7 (100 pF, 1500

)

3. EIAJ IC-121 (Condition C) (200 pF, 0

)

Symbol

Parameter

Value

Unit

Ambient Operating Temperature

0 to 70

°C

STG

Storage Temperature

-40 to 120

°C

Input or Output range

-0.6 to 6.5

Supply Voltage

-0.3 to 6.5

ESD

Electrostatic Discharge Voltage (Human Body model)

4000

Electrostatic Discharge Voltage (Machine model)

400

3/12

M14256, M14128

Write Control (WC)
The hardware Write Control contact (WC) is useful
for protecting the entire contents of the memory
from inadvertent erase/write. The Write Control
signal is used to enable (WC=V

) or disable

(WC=V

) write instructions to the entire memory

area. When unconnected, the WC input is internal-
ly read as V

and write operations are allowed.

When WC=1, Device Select and Address bytes
are acknowledged, Data bytes are not acknowl-
edged.
Please see the Application Note

AN404

for a more

detailed description of the Write Control feature.

DEVICE OPERATION
The memory device supports the XI

C (Extended

C) protocol, as summarized in Figure 4. Any de-

vice that sends data on to the bus is defined to be
a transmitter, and any device that reads the data
to be a receiver. The device that controls the data
transfer is known as the master, and the other as
the slave. A data transfer can only be initiated by
the master, which will also provide the serial clock
for synchronization. The memory device is always
a slave device in all communication.
Start Condition
START is identified by a high to low transition of
the SDA line while the clock, SCL, is stable in the
high state. A START condition must precede any
data transfer command. The memory device con-
tinuously monitors (except during a programming
cycle) the SDA and SCL lines for a START condi-
tion, and will not respond unless one is given.
Stop Condition
STOP is identified by a low to high transition of the
SDA line while the clock, SCL, is stable in the high

state. A STOP condition terminates communica-
tion between the memory device and the bus mas-
ter. A STOP condition at the end of a Read
command, after (and only after) a NoACK, forces
the memory device into its standby state. A STOP
condition at the end of a Write command triggers
the internal EEPROM write cycle.
Acknowledge Bit (ACK)

An acknowledge signal is used to indicate a suc-
cessful data transfer. The bus transmitter, either
master or slave, will release the SDA bus after
sending 8 bits of data. During the 9

clock pulse

period the receiver pulls the SDA bus low to ac-
knowledge the receipt of the 8 data bits.
Data Input
During data input, the memory device samples the
SDA bus signal on the rising edge of the clock,
SCL. For correct device operation, the SDA signal
must be stable during the clock low-to-high transi-
tion, and the data must change

only

when the SCL

line is low.
Memory Addressing

To start communication between the bus master
and the slave memory, the master must initiate a
START condition. Following this, the master sends
8 bits to the SDA bus line (with the most significant
bit first). These bits represent the Device Select
Code (7 bits) and a RW bit.
The seven most significant bits of the Device Se-
lect Code are the Device Type Identifier, according
to the I

C bus definition. For the memory device,

the seven bits are fixed at 1010000b (A0h), as
shown in Table 5.
The 8

bit is the read or write bit (RW). This bit is

set to `1' for read and `0' for write operations. If a
match occurs on the Device Select Code, the cor-

Figure 3. Maximum R

Value versus Bus Capacitance (C

BUS

) for an I

C Bus

AI01665

VCC

CBUS

SDA

MASTER

SCL

CBUS

100

CBUS (pF)

Maximum RP value (k

)

1000

fc = 400kHz

fc = 100kHz

M14256, M14128

4/12

responding memory gives an acknowledgment on
the SDA bus during the 9

bit time. If the memory

does not match the Device Select code, it will de-
select itself from the bus, and go into stand-by
mode.
Each data byte in the memory has a 16-bit (two
byte wide) address. The Most Significant Byte (Ta-
ble 3) is sent first, followed by the Least significant
Byte (Table 4). Bits b15 to b0 form the address of
the byte in memory. Bit b15 is treated as a Don't
Care bit on the M14256 memory. Bits b15 and b14
are treated as Don't Care bits on the M14128
memory.

Figure 4. I

C Bus Protocol

SCL

SDA

SCL

SDA

START

CONDITION

SDA

INPUT

SDA

CHANGE

AI00792

STOP

CONDITION

MSB

ACK

START

CONDITION

SCL

MSB

ACK

STOP

CONDITION

Table 5. Device Select Code

Note: 1. The most significant bit, b7, is sent first.

Device Code

Chip Enable

Device Select

Note: 1. b15 is Don't Care on the M14256 series.

b15 and b14 are Don't Care on the M14128 series.

Table 3. Most Significant Byte

b15

b14

b13

b12

b11

b10

Table 4. Least Significant Byte

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M14256, M14128

Figure 5. Write Mode Sequences with WC=1

STOP

START

BYTE WRITE

DEV SEL

BYTE ADDR

DATA IN

START

PAGE WRITE

DEV SEL

BYTE ADDR

DATA IN 1

DATA IN 2

AI01120B

PAGE WRITE
(cont'd)

WC (cont'd)

STOP

DATA IN N

ACK

NO ACK

R/W

ACK

NO ACK

R/W

NO ACK

Write Operations
Following a START condition the master sends a
Device Select code with the RW bit set to '0', as
shown in Table 6. The memory acknowledges it
and waits for two bytes of address, which provides
access to the memory area. After receipt of each
byte address, the memory again responds with an
acknowledge and waits for the data byte. Writing
in the memory may be inhibited if the input pin WC
is taken high.
Any write command with WC=1 (during a period of
time from the START condition until the end of the
two bytes address) will not modify the memory
content and will NOT be acknowledged on data
bytes, as shown in Figure 5.
Byte Write
In the Byte Write mode, after the Device Select
code and the address, the master sends one data
byte. If the addressed location is write protected by
the WC pin, the memory replies with a NoACK,
and the location is not modified. If, instead, the WC

pin has been held at 0, as shown in Figure 6, the
memory replies with an ACK. The master termi-
nates the transfer by generating a STOP condi-
tion.
Page Write
The Page Write mode allows up to 64 bytes to be
written in a single write cycle, provided that they
are all located in the same 'row' in the memory:
that is the most significant memory address bits
(b14-b6 for the M14256 and b13-b6 for the
M14128) are the same. The master sends from
one up to 64 bytes of data, each of which is ac-
knowledged by the memory if the WC pin is low. If
the WC pin is high, each data byte is followed by a
NoACK and the location is not modified. After each
byte is transferred, the internal byte address coun-
ter (the six least significant bits only) is increment-
ed. The transfer is terminated by the master
generating a STOP condition. Care must be taken
to avoid address counter 'roll-over' which could re-
sult in data being overwritten. Note that, for any

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