M95160-RMN5 データシートの表示（PDF） - STMicroelectronics

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M95160-RMN5

64/32/16/8 Kbit Serial SPI Bus EEPROM With High Speed Clock

STMicroelectronics 

M95640, M95320, M95160, M95080

Table 6. Write Protected Block Size

Status Register Bits

Protected Block

BP1

BP0

M95640

0

0

none

none

0

1

Upper quarter 1800h - 1FFFh

1

0

Upper half

1000h - 1FFFh

1

1

Whole memory 0000h - 1FFFh

Array Addresses Protected

M95320

M95160

none

none

0C00h - 0FFFh 0600h - 07FFh

0800h - 0FFFh 0400h - 07FFh

0000h - 0FFFh 0000h - 07FFh

M95080

none

0300h - 03FFh

0200h - 03FFh

0000h - 03FFh

ray and to the SRWD, BP1 and BP0 bits of the sta-

tus register, provided that the WEL bit is first set.

Hardware Protected Mode (HPM)

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 instruc-

tion, provided that the WEL bit is first set. The set-

ting 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 regis-

ter, are write-protected. The only way to re-enable

writing new values to the status 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) are 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 VSS (by a sol-

der connection, or through a pull-down resistor).

The manufacturer of such a printed circuit board

can take the memory device, still in its initial deliv-

ery state, and can solder it directly on to the board.

After power on, the microcontroller can be instruct-

ed to write the protected data into the appropriate

area of the memory. When it has finished, the ap-

propriate values are written to the BP1, BP0 and

SRWD bits, thereby putting the device in the hard-

ware protected mode.

An alternative method is to write the protected da-

ta, and to set the BP1, BP0 and SRWD bits, before

soldering the memory device to the board. Again,

this results in the memory device being placed in

its hardware protected mode.

If the W pin has been connected to VSS by a pull-

down resistor, the memory device can be taken

out of the hardware protected mode by driving the

W pin high, to override the pull-down resistor.

If the W pin has been directly soldered to VSS,

there is only one way of taking the memory device

out of the hardware protected mode: the memory

Figure 7. WRSR: Write Status Register Sequence

S

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

C

INSTRUCTION

STATUS REG.

D

76543210

MSB

HIGH IMPEDANCE

Q

AI02282

7/19

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