SE97TP datasheet(20/55 Pages) NXP

20 / 55 page

SE97_7

Product data sheet

Rev. 07 — 29 January 2010

20 of 55

NXP Semiconductors

SE97

DDR memory module temp sensor with integrated SPD, 3.3 V

7.10.2.1

Permanent Write Protection (PWP)

If the software write-protection has been set with the PWP instruction, the first 128 bytes

of the memory are permanently write-protected. This write-protection cannot be cleared

by any instruction, or by power-cycling the device. Also, once the PWP instruction has

been successfully executed, the device no longer acknowledges any instruction (with 4-bit

fixed address of 0110b) to access the write-protection settings.

7.10.2.2

Reversible Write Protection (RWP) and Clear Reversible Write Protection (CRWP)

If the software write-protection has been set with the RWP instruction, it can be cleared

again with a CRWP instruction.

The two instructions, RWP and CRWP have the same format as a Byte Write instruction,

but with a different setting for the hardware address pins (as shown in Table 5). Like the

Byte Write instruction, it is followed by an address byte and a data byte, but in this case

the contents are all ‘Don’t Care’ (Figure 17). Another difference is that the voltage, VI(ov),

must be applied on the A0 pin, and specific logical levels must be applied on the other two

(A1 and A2), as shown in Table 5.

X = Don’t Care

(1) Refer to Table 7 regarding the exact state of the acknowledge bit.

Fig 18. Software Write Protect (read)

A2 A1 A0

slave address (memory)

START condition

R/W acknowledge(1)

from slave

no acknowledge(1)

from slave

dummy byte address

SDA

dummy data

no acknowledge(1)

from slave

002aac644

STOP condition

XXXXXXXX

Table 6.

Acknowledge when writing data or defining write protection

Instructions with R/W bit = 0.

Status

Instruction

ACK

Address

ACK

Data byte

ACK

Write cycle

(Tcy(W))

Permanently

protected

PWP, RWP or CRWP

NACK

not significant

NACK

not significant

NACK

page or byte write in

lower 128 bytes

ACK

address

ACK

data

NACK

Protected with

RWP

NACK

not significant

NACK

not significant

NACK

CRWP

ACK

not significant

ACK

not significant

ACK

yes

PWP

ACK

not significant

ACK

not significant

ACK

yes

page or byte write in

lower 128 bytes

ACK

address

ACK

data

NACK

Not protected

PWP or RWP

ACK

not significant

ACK

not significant

ACK

yes

CRWP

ACK

not significant

ACK

not significant

ACK

page or byte write

ACK

address

ACK

data

ACK

yes

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