STMicroelectronics M95040, M95020, M95010 User Manual

4Kbit, 2Kbit and 1Kbit Serial SPI Bus EEPROM

FEAT URES SUM MAR Y

■ Compatible with SPI Bus Serial Interface

(Positive Clock SPI Modes)

■ Single Supply Voltage:

– 4.5 to 5.5V for M950x0
– 2.5 to 5.5V for M950x0-W
– 1.8 to 5.5V for M950x0-R

■ High Speed

– 10MHz Clock Rate, 5ms Write Time

■ Status Register

■ BYTE and PAGE WRITE (up to 16 Bytes)

■ Self-Timed Programming Cycle

■ Adjustable Size Read-Only EEPROM Area

■ Enhanced ESD Protection

■ More than 1 Million Erase/Write Cycles

■ More than 40-Year Data Retention

M95040

M95020, M95010

With High Speed Clock

Figure 1. Packages

8

1

PDIP8 (BN)

8

Table 1. Product List

Reference Part Number

M95040

M95020

M95010

M95040
M95040-W
M95040-R
M95020
M95020-W
M95020-R
M95010
M95010-W
M95010-R

1

SO8 (MN)

150 mil width

TSSOP8 (DW)

169 mil width

1/37October 2004

M95040, M95020, M95010

TABLE OF CONTENTS

FEATURES SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Table 1. Product List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Figure 1. Packages. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

SUMMARY DESCRIPTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Figure 2. Logic Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Figure 3. DIP, SO and TSSOP Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Table 2. Signal Names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

SIGNAL DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Serial Data Output (Q). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Serial Data Input (D) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Serial Clock (C) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6

Chip Select (S) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Hold (HOLD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Write Protect (W). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

CONNECTING TO THE SPI BUS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Figure 4. Bus Master and Memory Devices on the SPI Bus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

SPI Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Figure 5. SPI Modes Supported . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

OPERATING FEATURES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Power-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Power-down. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Active Power and Standby Power Modes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Hold Condition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Figure 6. Hold Condition Activation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Status Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

WIP bit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

WEL bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

BP1, BP0 bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Table 3. Status Register Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Data Protection and Protocol Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Table 4. Write-Protected Block Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

MEMORY ORGANIZATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Figure 7. Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Table 5. Instruction Set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Write Enable (WREN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Figure 8. Write Enable (WREN) Sequence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

2/37

M95040, M95020, M95010

Write Disable (WRDI). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Figure 9. Write Disable (WRDI) Sequence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Read Status Register (RDSR). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

WIP bit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

WEL bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

BP1, BP0 bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Figure 10.Read Status Register (RDSR) Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Write Status Register (WRSR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Figure 11.Write Status Register (WRSR) Sequence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Read from Memory Array (READ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Table 6. Address Range Bits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Figure 12.Read from Memory Array (READ) Sequen ce . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Write to Memory Array (WRITE). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

Figure 13.Byte Write (WRITE) Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Figure 14.Page Write (WRITE) Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

POWER-UP AND DELIVERY STATE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Power-up State . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Initial Delivery State . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

MAXIMUM RATING. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Table 7. Absolute Maximum Ratings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

DC AND AC PARAMETERS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1

Table 8. Operating Conditions (M950x0). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Table 9. Operating Conditions (M950x0-W) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Table 10. Operating Conditions (M950x 0-R). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Table 11. AC Measurement Condition s. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

Figure 15.AC Measurement I/O Waveform. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Table 12.Capacitance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Table 13. DC Characteristics (M950x0, Device Grade 6) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Table 14. DC Characteristics (M950x0, Device Grade 3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Table 15. DC Characteristics (M950x0-W, Device Grade 6). . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23

Table 16. DC Characteristics (M950x0-W, Device Grade 3). . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

Table 17. DC Characteristics (M950x0-R). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Table 18. AC Characteristics (M950x0, Device Grade 6) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Table 19. AC Characteristics (M950x0, Device Grade 3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Table 20. AC Characteristics (M950x0-W, Device Grade 6) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Table 21. AC Characteristics (M950x0-W, Device Grade 3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Table 22. AC Characteristics (M950x0-R). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Figure 16.Serial Input Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Figure 17.Hold Timing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Figure 18.Output Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

PACKAGE MECHANICAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Figure 19.PDIP8 – 8 pin Plastic DIP, 0.25mm lead frame, Package Outline . . . . . . . . . . . . . . . . . 32

3/37

M95040, M95020, M95010

Table 23. PDIP8 – 8 pin Plastic DIP, 0.25mm lead frame, Package Mechanical Data . . . . . . . . . . 32

Figure 20.SO8 narrow – 8 lead Plastic Small Outline, 150 mils body width, Package Outline . . . . 33

Table 24. SO8 narrow – 8 lead Plastic Small Outline, 150 mils body width, Package Mechanical Data
33

Figure 21.TSSOP8 – 8 lead Thin Shrink Small Outline, Package Outline . . . . . . . . . . . . . . . . . . . 34

Table 25. TSSOP8 – 8 lead Thin Shrink Sma ll Outline, Packag e Mechanica l Data . . . . . . . . . . . . 34

PART NUMBERING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Table 26.Ordering Information Scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Table 27. How to Identify Present and Previous Pro ducts by the Process Identi fication Letter . . . 35

REVISION HISTORY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Table 28. Document Revision History. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

4/37

SUMMARY DESCRIPTION

The M95040 is a 4 Kbit (512 x 8) electrically eras­able programmable memory (EEPROM), access­ed by a high speed SPI-compatible bus. The other
members of the family (M95020 and M95010 ) are
identical, though proportionally smaller (2 and 1
Kbit, respe c ti v e ly).

Each device is accessed by a sim ple serial inter­face that is SPI-compatible. The bus signals are C,
D and Q, as shown in Table 2. and F igure 2..

The device is selected when Chip Select (S
en Low. Communications with the devi ce can be
interrupted using Hold (HOLD

). WRITE instruc-

tions are disabled by Write Protect (W

Figure 2. Logic Diagram

V

CC

D
C
S

W

M95xxx

) is tak-

).

Q

M95040, M95020, M95010

Figure 3. DIP, SO and TSSOP Connections

M95xxx

SV

1
2

W

3
4

SS

Note: See PACKAGE MECHANICAL section for package dimen-

sions, and how to ident i fy pi n-1.

Table 2. Signal Names

C Serial Clock
D Serial Data Input
Q Serial Data Output

S

Write Protect

W

Chip Select

8
7
6
5

AI01790D

CC

HOLDQ
C
DV

HOLD

HOLD

Hold

V

CC

V

V

SS

AI01789C

SS

Supply Voltage
Ground

5/37

M95040, M95020, M95010

SIGNAL DESCRIPTION

During all operations, VCC must be held stable and
within the specified valid range: V

(max).

V

CC

All of the input and output signals can be held High
or Low (according to voltage s of V

, as specified in Table 13. to Table 17.). These

V

OL

signals are described next.
Serial Data Output (Q). This output signal is

used to transfer data serially out of the device.
Data is shifted out on the falling edge of Serial
Clock (C).

Serial Data Input (D). This input signal is used to
transfer data serially into the device. It receives in­structions, addresses, and the data to be written.
Values are latched on the rising edge of Serial
Clock (C).

Serial Clock (C). This input signal provides the
timing of the serial interface. Instructions, address­es, or data present at Serial Data Input (D) are
latched on the rising edge of Serial Clock (C). Data
on Serial Data Output (Q) changes after the falling
edge of Serial Clock (C).

(min) to

CC

, VOH, VIL or

IH

Chip Select (S

). When this input signal is High,

the device is des elected and Serial Data Ou tput
(Q) is at high impedance. Unless an internal Write
cycle is in progress, the device will be in the Stand­by Power mode. Drivi ng Chip Select ( S

) Low se­lects the device, placing it in the Active Power
mode.

After Power-up, a falling edge on Chip Select (S
is required prior to the start of any instruction.

Hold (HOLD

). The Hold (HOLD) signal is used to

pause any serial communications with the device
without deselecting the device.

During the Hold condition, the Serial Data Output
(Q) is high impedanc e, and Serial D ata Input (D)
and Serial Clock (C) are Don’t Care.

To start the Hold condition, the device must be se­lected, wit h Ch ip Select ( S

Write Protect (W

). This input signal is used to

) driven Low.

control whether the memory is write protected.
When Write Protect (W

) is held Low, writes to the
memory are disabled, but other operations remain
enabled. Write Protect (W

) must either be driven

High or Low, but must not be left floating.

)

6/37

CONNECTI NG TO THE SPI BUS

These devices are fully compatible with the SPI
protocol.

All instructions, addresses and input data bytes
are shifted in to the device, most significant bit
first. The Serial Data Input (D) is sampled on the
first rising edge of the Serial Clock (C) after Chip
Selec t ( S

) goes Low.

All output data bytes are shifted out of the device,
most significant bit first. The Serial Data Output

Figure 4. Bus Master and Memory Devices on the SPI Bus

(Q) is latched on the first fa lling edge of the Serial
Clock (C) after the instruction (such as the Read
from Memory Array and Read Status Re gister in­structions) have been clocked into the device.

Figure 4 . shows three devices, con nected to an

MCU, on a SPI bus. Only one device is selected at
a time, so only one de vice drives the Serial Data
Output (Q) line at a time, all the o thers be ing high
impedance.

M95040, M95020, M95010

SPI Interface with

(CPOL, CPHA) =

(0, 0) or (1, 1)

Bus Master

(ST6, ST7, ST9,

ST10, Others)

CS3 CS2 CS1

Note: The Write Protect (W) and Hold (HOLD) signals should be dri ven, High or Low as appropriat e.

SDO
SDI
SCK

CQD

SPI Memory

Device

S

CQD

SPI Memory

Device

HOLD

W

S

HOLD

W

CQD

SPI Memory

Device

S

W

AI03746D

HOLD

7/37

M95040, M95020, M95010

SPI Modes

These devices can be drive n by a microcont roller
with its SPI peripheral running in either of the two
following modes:

– CPOL=0, CPHA=0
– CPOL=1, CPHA=1
For these two modes, input data is latc hed in on

the rising edge of Serial Clock (C), and output data

Figure 5. SPI Mo de s S upported

CPHA

CPOL

0

0

1

1

C

C

D

Q

MSB

is avai lable from t he falling edge of S erial Clock
(C).

The difference between the two modes, as shown
in Figure 5., is the clock polarity when the bus
master is in Stand-by mode and not transferring
data:

– C remains at 0 for (CPOL=0, CPHA=0)
– C remains at 1 for (CPOL=1, CPHA=1)

MSB

AI01438B

8/37

OPERATING FEA T URES

Power-up

When the power supply is turned on, V
from V

During this time, the Chip Select (S
lowed to follow the V

to VCC.

SS

) must be al-

voltage. It must not be al-

CC

lowed to float, but should be connected to V
a suitable pull-up resistor.

As a built in safety feature, Chip Select (S
sensitive as well a s level sens itive. After P ower­up, the device does not become s elected until a
falling edge has first been detected on Chip Select

). This ensures that Ch ip Select (S) must have

(S
been High, prior to going Low to start the first op­eration.

Power-down

At Power-down, the device must be deselected.
Chip Select (S
voltage applied on V

) should be allowed to follow the

.

CC

Active Power and Standb y Power M ode s

When Chip Select (S

) is Low, the device is select­ed, and in the Active Power mode. The device
consumes I

, as specified in Table 13. to Table

CC

17..

When Chip Select (S

) is High, the device is dese­lected. If an Erase/Write cycle is not currently in
progress, the device then goes in to the Standby

rises

CC

via

CC

) is edge

M95040, M95020, M95010

Power mode, and the device cons umption drops

CC1

.

) signal is used to pause any se-

) Low.

to I

Hold Condition

The Hold (HOLD
rial communications with the device without reset­ting the clocking sequence.

During the Hold condition, the Serial Data Output
(Q) is high impedanc e, and Serial D ata Input (D)
and Serial Clock (C) are Don’t Care.

To enter the Hold condition, the device must be
selecte d, with Chip Se lec t (S

Normally, the device is kept selected, for the whole
duration of the Hold condition. Deselecting the de­vice while it is in the Hold condition, has the effect
of resetting the state of the device, and this mech­anism can be used if it is required to reset any pro­cesses that had been in progress.

The Hold condition starts when the Hold (HOLD
signal is driven Low at the same time as Serial
Clock (C) already being Low (as shown in Figure

6.).

The Hold condition ends when the Hold (HOLD
signal is driven High at the same time as Serial
Clock (C) already being Low.

Figure 6 . also shows what happens if the rising

and falling edges are not timed to coincide with
Serial Clock (C) being Low.

)

)

Figure 6. Hold Condition Activation

C

HOLD

Hold

Condition

Hold

Condition

AI02029D

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M95040, M95020, M95010

Status Register

Figure 7. shows the position of the Status Register

in the control logic of the device. This register con­tains a number of c ontrol bits and status bits, as
shown in Table 3..

Bits b7, b6, b5 and b4 are always read as 1.
WIP bit. The Write In Progress bit is a volatile

read-only bit that is automatically set and reset by
the internal logic of the device. When s et to a 1 , it
indicates that the memory is busy with a Write cy­cle.

WEL bit. The Write Enable Latch bit is a vol atile
read-only bit that is set and reset by specific in­structions. When reset to 0, no WRITE or WRSR
instructions are accepted by the device.

BP1, BP0 bits. The Block Protect bits are non­volatile read-write bits. These bits define the area
of memory that is protected against the execution
of Write cycles, as summarized in Table 4..

Table 3. Status Register Format

b7 b0

1 1 1 1 BP1 BP0 WEL WIP

Block Protect Bits

Write Enable Latch Bit

Write In Progress Bit

Data Protec ti on a n d Protocol Cont rol

To help protect t he d ev ice from data corruption in
noisy or poorly controlled environments, a number
of safety features have been built in to the device.
The main security measures can be summarized
as follows:

– The WEL bit is reset at power-up.
– Chip Select (S

) must rise after the eighth clock
count (or multiple thereof) in order to start a
non-volatile Write cycle (in the memory array
or in the Status Register).

– Accesses to the memory array are ignored

during the non-volatile programming cycle,
and the programming cycle continues
unaffected.

– Invalid Chip Select (S

) and Hold (HOLD)

transitions are ignored.

For any instruction to be accepted and executed,
Chip Select (S

) must be driven High after the rising
edge of Serial Clock (C) that latches the last bit of
the instruction, and before the next rising edge of
Serial Clock (C).

For this, “the last bit of the instruction” can be the
eighth bit of the instruction code, or the ei ghth bit
of a data byte, depending on the instruction (ex­cept in the case of RDSR and READ instructions).
Moreover, the "next rising edge of CLOCK" might
(or might not) be the next bus transaction for some
other device on the bus.

When a Write cycle is in progress, the device pro­tects it against external interruption by ignoring
any subsequent READ, WRITE or WRSR instruc­tion until the presen t cycl e is complete.

Table 4. Write-Protected Block Size

Status Register Bits

Protected Block

BP1 BP0 M95040 M95020 M95010

0 0 none none none none
0 1 Upper quarter 180h - 1FFh C0h - FFh 60h - 7Fh
1 0 Upper half 100h - 1FFh 80h - FFh 40h - 7Fh
1 1 Whole memory 000h - 1FFh 00h - FFh 00h - 7Fh

10/37

Array Addresses Protected

MEMOR Y ORGANIZATION

The memory is organized as shown in Figure 7..

Figure 7. Block Diagram

M95040, M95020, M95010

HOLD

W

S

C

D

Q

Control Logic

I/O Shift Register

Address Register

and Counter

Y Decoder

High Voltage

Generator

Data

Register

1 Page

Status

Register

Size of the
Read only
EEPROM
area

X Decoder

AI01272C

11/37

M95040, M95020, M95010

INSTRUCTIONS

Each instruction starts with a single-byte code, as
summarized in Table 5..

If an invalid instruction is s ent (one not con tained
in Table 5.), the device automatically deselects it­self.

Table 5. Instruction Set

Instruc

tion

WREN Write Enable 0000 X110
WRDI Write Disable 0000 X100
RDSR Read Status Register 0000 X101
WRSR Write Status Register 0000 X001
READ Read from Memory Array
WRITE Write to Memory Array

Note: 1. A8 = 1 for the upper half of the memory array of the

M95040, and 0 for the lower half, and is Don’t Care fo r
other devices.

2. X = Don’ t Care.

Description

Instruction

Format

0000 A
0000 A

8

8

011
010

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