SGS Thomson Microelectronics M95256-RMW5T, M95256-R, M95256, M95128-W, M95256-W Datasheet

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PRELIMINARY DATA

March 2000

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

M95256 M95128

256/128 Kbit Serial SPI Bus EEPROM

With High Speed Clock

■ SPI Bus Compatible Serial Interface

■ Supports Positive Clock SPI Modes

■ 5 MHz Clock Rate (maximum)

■ Single Supply Voltage:

– 4.5V to 5.5V for M95xxx – 2.7V to 3.6V for M95xxx-V – 2.5V to 5.5V for M95xxx-W – 1.8V to 3.6V for M95xxx-R

■ Status Register

■ Hardware and Software Protection of the Status

■ BYTE and PAGE WRITE (up to 64 Bytes)

■ Self-Tim ed P ro gr a m ming Cycle

■ Resizeable Read-Only EEPROM Area

■ Enhanced ESD Protection

■ 100,000 Erase/Write Cycles (minimum)

■ 40 Year Data Retention (minimum)

DESCRIPTION

These SPI-compatible electrically erasable programmable memory (EEPROM) devices are organized as 32K x 8 bits (M9525 6) and 16K x 8 bits (M95128), and operate down to 2.7 V (for the

Figure 1. Logic Diagram

AI01789C

M95xxx

HOLD

Table 1. Signal Names

C Serial Clock D Serial Data Input Q Serial Data Output

Chip Select

Write Protect

HOLD

Hold

Supply Voltage

Ground

PSDIP8 (BN)

0.25 mm frame

SO8 (MN)

150 mil width

TSSOP14 (DL)

169 mil width

SO8 (MW)

200 mil width

M95256, M95128

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-V version), 2.5 V (for the -W version), and down to 1.8 V (for the -R version of each device).

The M95256 and M 95128 are available in Plastic Dual-in-Line, Plastic Small Outline and Thin Shrink Small Outline packages.

Each memory device is accessed by a simple serial interface that is SPI bus compatible. The bus signals are C, D and Q, as shown in Table 1 and Figure 3.

The device is selected when t he chip select input (S

) is held low. Communications with the chip can

be interrupted using the hold input (HOLD

Figure 2A. DIP Connections

Figure 2B. SO C on ne ct i on s

HOLDQ

AI01790C

M95xxx

1 2 3 4

8 7 6 5

AI01791C

2 3 4

8 7 6 5

HOLDQ

M95xxx

Figure 2C. TSSOP Connections

Note: 1. NC = Not Connected

AI02346

2 3 4

HOLD

M95128

NC NC

5 6 7

Table 2. Absolute Maximum Ratings

Note: 1. Except for the rating “Operating Tempera ture Range”, stres ses above th ose listed i n the Tabl e “Absolute Maxim um 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 conditions for extended periods may affect device reliability. Refer also to the ST SURE Program and other relevant quality document s.

2. M IL-STD-883C, 3015.7 (100 pF, 1500 Ω)

Symbol Parameter Value Unit

Ambient Operating Temperature -40 to 125 °C

STG

Storage Temperature -65 to 150 °C

LEAD

Lead Temperature during Soldering

PSDIP8: 10 sec SO8: 40 sec TSSOP14: t.b.c.

260 215

t.b.c.

°C

Output Voltage Range

-0.3 to V

+0.6

Input Voltage Range -0.3 to 6.5 V

Supply Voltage Range -0.3 to 6.5 V

ESD

Electrostatic Discharge Voltage (Human Body model)

4000 V

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M95256, M95128

SIGNAL DESCRIPTION Seria l O utput ( Q )

The output pin is used to transfer data serially out of the Memory. Data is shifted out on the falling edge of the serial clock.

Serial Inpu t ( D )

The input pin is used to transfer data serially into the device. Instructions, addresses, and the data to be written, are each received this way . Input is latched on the rising edge of the serial clock.

Serial Clock (C)

The serial clock provides the timing for the serial interface (as shown in Figure 4). Instructions, addresses, or data are latched, from the input pin, on the rising edge of the clock input. The output data on the Q pin chang es state after the falling edge of the clock input.

Chip Select (S

)

When S

is high, the memory device is deselected, and the Q output pin is held in its high impe dance state. Unless an internal write operation is underway, the memory device is placed in its stand-by power mode.

After power-on, a high-to-low transition on S

required prior to the start of any operation.

Write Protect (W

)

The protection features of t he m em ory device are summarized in Table 3.

The hardware write protection, controlled by the W pin, restricts write access to the Status Register

(though not to the WIP and WEL bits, which are set or reset by the device internal logic).

Bit 7 of the status register (as shown in Table 5) is the Status Register Write Disable bit (SRWD). When this is set to 0 (its initial delivery state) it is possible to write to the status register if the WEL bit (Write Enable Latch) has been set by the WREN instruction (irrespective of the l evel being applied to the W

input).

When bit 7 (SRWD) of the st atus register is set to 1, the ability to write to the status register depends on the logic level being presented at pin W

–If W

pin is high, it is possible to write to the status register, after having set the WEL bit using the WREN instruction (Write Enable Latch).

–If W

pin is low, any attempt to modify the status register is ignored by the device, even if the WEL bit has been set. As a consequence, all the data bytes in the EE PROM area, protected by the BPn bits of the status register, are also hardware protected against data corruption, and appear as a Read Only EEPROM area for the microcontroller. This mode is called the Hardware Protected Mode (HPM).

It is possible to enter the Hardware Protected Mode (HPM) either by s etting the SRWD bi t after pulling low the W

pin, or by pulling low the W pin

after setting the SRWD bit. The only way to abort the Hardware Protected

Mode, once entered, is to pull high the W

pin.

If W

pin is permanently t ied to the hi gh level, the

Hardware Protected Mode is never activated, and

Figure 3. Microcontroller and Memor y Devices on the SPI Bus

AI01958C

Master

(ST6, ST7, ST9,

ST10, Others)

M95xxx

SDO

SDI

SCK

CQD

M95xxx

CQD

M95xxx

CQD

CS3 CS2 CS1

SPI Interface with (CPOL, CPHA) = ('0', '0') or ('1', '1')

M95256, M95128

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the memory device only allows the user to protect a part of the memory, usi ng the BPn bits of the status register, in the Software Protected Mode (SPM).

Hold (HOLD

)

The HOLD

pin is used to pause the serial communications between the SPI memory and controller, without losing bits that have already been decoded in the serial sequence. For a hold condition to occur, the memory device must already have been selected (S

= 0). The hold

condition starts when the HOLD

pin is held low while the clock pin (C) is also low (as shown in Figure 5).

During the hold condition, the Q output pin i s held in its high impedance sta te, and the level s on the input pins (D and C) are ignored by the memory device.

It is possible to deselect the device whe n it is still in the hold state, thereby resetting whatever transfer had been in progress. The memory remains in the hold state as long as the HOLD

pin is low. To restart communication with the device, it is necessary both to remove the hold condition (by takin g HO LD

high) and to select the memory (by

taking S

low).

OPERATIONS

All instructions, addresses and data are shifted serially in and out of the chip. The most significant bit is presented first, with the data input (D) sampled on the first rising edge of the clock (C) after the chip select (S

) goes low.

Every instruction starts with a single-byte code, as summarized in Table 4. This code is entered via the data input (D), and latched on the rising edge of the clock input (C). To enter an instruction code, the product must have been previously selected (S held low). If an invalid i nstruction is sent (one not contained in Table 4), the chip automatically deselects itself.

Write Enable (WREN) and Write Disable (WRDI)

The write enable latch, inside the memory device, must be set prior to each WRITE and WRSR operation. The WREN instruction (write enable) sets this latch, and the WRDI instruction (write disable) resets it.

The latch becomes reset by any of the following events:

– Power on – WRDI instruction completion – WRSR in s t ru ctio n completio n – WRITE instruction completion.

Table 3. Write Protection Control on the M95256 and M95128

SRWD

Bit

Mode Status Register

Data Bytes

Protected Area Unprotected Area

0 or 1 0 Software

Protected

(SPM)

Writeable (if the WREN

instruction has set the

WEL bit)

Software write protected

by the BPn of the status

Writeable (if the WREN

instruction has set the

WEL bit)

Hardware Protected

(HPM)

Hardware write protected

by the BPn bits of the

status register

Writeable (if the WREN

instruction has set the

WEL bit)

Figure 4. Dat a and Clock Timi ng

AI01438

MSB LSB

CPHA

D or Q

CPOL

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M95256, M95128

Figure 5. Hold Condition Activation

Figure 6. Block Diagram

Note: 1. The cell

represents the byte at the highest address in the memory

AI02029B

HOLD PIN

CLOCK

ACTIVE

MEMORY STATUS

HOLD ACTIVE HOLD ACTIVE

AI02030B

HOLD

Control Logic

High Voltage

Generator

I/O Shift Register

Address Register

and Counter

Data

64 Bytes

X Decoder

Y Decoder

Size of the Read only area of the EEPROM

Status

AnAn - 63

003Fh0000h

M95256, M95128

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As soon as the WREN or WRDI instruction is received, the memory device first executes the instruction, then enters a wait mode until the device is deselected.

Read Status Register (RDSR)

The RDSR instruction allows the status register to be read, and can be sent at any time, even during a Write operation. Indeed, when a Write is in progress, it is recommended th at the value of t he Write-In-Progress (WIP) bit be checked. The value in the WIP bit (whose position in the status register is shown in Table 5) can be continuously p olled, before sending a new WRITE instruction, using the timing shown in Figure 7. The Write-InProcess (WIP) bit is read-only, and indicates whether the memory is busy with a Write

operation. A ’1’ indicates that a write is in progress, and a ’0’ that no write is in progress.

The Write Enable Latch (WEL) bit indicates the status of the write enable latch. It, too, is read-only.

Its value can only be changed by one of the events listed in the previous paragraph, or as a result of executing WREN or WRDI instruction. It cannot be changed using a WRSR instruction. A ’1’ indicates that the latch is set (the forthcoming Write instruction will be executed), and a ’0’ that it is reset (and any forthcoming Write instructions will be ignored).

The Block Protect (BP0 and BP1) bits indicate the amount of the memory that is to be writeprotected. These two bits are non-volatile. They are set using a WRSR instruction.

During a Write operation (whether it be to the memory area or to the status register), all bits of the status register remain valid, and can be read using the RDSR instruction. However, during a Write operation, the values of the no n-vo latile bits (SRWD, BP0, BP1) be come frozen at a constant value. The updated value of these bi ts becomes available when a new RDSR instruction is executed, after completio n of the write cycle. On the other hand, the two read-only bits (WEL, WIP) are dynamically updated during internal write cycles. U sing t his fac ility, it is possib le to p oll the WIP bit to detect the end of the internal write cycle.

Write Status Register (WRSR)

The format of the WRSR instruction is shown in Figure 8. After the instruction and the eigh t bits of the status register have been latched-in, the internal Write cycle is triggered by the rising edge of the S

line. This must occur before the rising

edge of the 17

clock pulse (as indicated in Figure

14), otherwise the internal write sequence is not performed.

The WRSR instruction is used for the following:

■ to select the size of memory area that is to be

write-protected

■ to select between SPM (Software Protected

Mode) and HPM (Hardware Protected Mode).

Figure 7. RDSR: Read Status Register Sequence

21 3456789101112131415

INSTRUCTION

AI02031

7 6543210

STATUS REG. OUT

HIGH IMPEDANCE

MSB

7 6543210

STATUS REG. OUT

MSB MSB

Table 4. Instruction Set

Table 5. Status Register Format

Note: 1. SRWD, BP0 and BP1 are Read and wri te bits.

2. WEL and WIP are Read only bits.

Instruc

tion

Description

Instruction

Format

WREN Set Write Enable Latch 0000 0110 WRDI Reset Write Enable Latch 0000 0100 RDSR Read Status Register 0000 0101 WRSR Write Status Register 0000 0001 READ Read Data from Memory Array 0000 0011 WRITE Write Data to Memory Array 0000 0010

b7 b0

SRWD X X X BP1 BP0 WEL WIP

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M95256, M95128

The size of the write-protection area applies equally in SPM and HPM. The BP1 and BP0 bits of the status register have the appropriate value (see Table 6) written into them after the contents of the protected area of the EEPROM have been written.

The initial delivery state of the BP1 and BP0 bits is 00, indicating a write-protection size of 0.

Software Protected Mode (SPM)

The act of writing a non-zero value to the BP1 and BP0 bits causes the Software Protected Mode (SPM) to be started. All attempts to write a byte or page in the protected area are ignored, even if the Write Enable Latch is set. However, writing is still allowed in the unprotected area of the memory array and to the SRWD, BP 1 and BP 0 bits of the status register, provided that the WEL bit is first set.

Hardware Prot ected Mode (H P M)

The Hardware Protected Mode (HPM) offers a higher level of protection, and can be selected by setting the SRWD bit after pulling down the W

pin or by pulling down the W

pin after setting the SRWD bit. The SRWD is set by the WSR instruction, provided that the WEL bit is first set.

The setting of the SRWD bit can be made independently of, or at the same time as, writing a new value to the BP1 and BP0 bits.

Once the device is in the Hardware Protected Mode, the data bytes in the protected area of the memory array,

and

the content of the status register, are write-protected. The only way to reenable writing new v alue s t o t he s tatus register is to pull the W

pin high. This cause the device to leave the Hardware Protected Mode, and to revert to being in the Software Protected Mode. (The value in the BP1 and BP0 bits will not have been changed).

Further details of the operation of the Write Protect pin (W

) is given earlier, on page 3.

Typical Use of HPM and SPM

The W

pin can be dynamically driven by an output port of a microcontroller. It is also possible, though, to connect it permanently to V

(by a solder connection, or through a pull-down resistor). The manufacturer of such a printed circuit board can take the memory device, still in its initial delivery state, and can solder it directly on to the board. After power on, the microcontroller can be instructed to write the protected data into the

Table 6. Write Protected Block Size

Status Register Bits

Protected Block

Array Addresses Protected

BP1 BP0 M95256 M95128

0 0 none none none 0 1 Upper quarter 6000h - 7FFFh 3000h - 3FFFh 1 0 Upper half 4000h - 7FFFh 2000h - 3FFFh 1 1 Whole memory 0000h - 7FFFh 0000h - 3FFFh

Figure 8. WRSR: Write Status Register Sequence

AI02282

21 3456789101112131415

HIGH IMPEDANCE

INSTRUCTION STATUS REG.

765432 0

MSB

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