X24F064/032/016

9

PROGRAM PROTECT REGISTER

The Program Protect Register (PPR) is accessed at the

highest address of each device:

X24F064 = 1FFF

X24F032 = 0FFF

X24F016 = 07FF

Figure 10. Program Protect Register

PPR.1 = WEL

–

Write Enable Latch (Volatile)

0 = Write enable latch reset, programming disabled

1 = Write enable latch set, programming enabled

If WEL = 0 then “no ACK” after first byte of input data.

PPR.2 = RWEL

–

Register Write Enable Latch (Volatile)

0 = Register write enable latch reset, programming

disabled

1 = Register write enable latch set, programming

enabled

PPR.3, PPR.4 = BL0, BL1

–

Block Lock Bits (Nonvolatile)

(See Block Lock Bits section for definition)

PPR.7 = PPEN

–

Programming Protect Enable Bit (Nonvolatile)

(See Programmable Hardware Program Protect sec-

tion for definition)

Writing to the Program Protect Register

The Program Protect Register is written by performing

a write of one byte directly to the highest address loca-

tion. During normal Sector Programming, the byte in

the array at the highest address will be written instead

of the Program Protect Register (assuming program-

ming is not disabled by the Block Lock register).

The state of the Program Protect Register can be read

by performing a random read at the highest address

location at any time. If a sequential read starting at any

7

6

5

4

3

2

1

0

PPEN

0

0

BL1

BL0

RWEL

WEL

0

6686 ILL F15

other address than the highest address location is

performed, the contents of the byte in the array at the

highest address location is read out instead of the

Program Protect Register.

WEL and RWEL are volatile latches that power-up in

the LOW (disabled) state. A write to any address other

than the highest address location, where the Program

Protect Register is located, will be ignored (no ACK)

until the WEL bit is set HIGH. The WEL bit is set by

writing 0000001x to the highest address location.

Once set, WEL remains HIGH until either reset (by

writing 00000000 to the highest address location) or

until the part powers-up again. The RWEL bit controls

writes to the Block Lock bits. RWEL is set by first

setting WEL = 1 and then writing 0000011x to the

highest address location. RWEL must be set in order

to change the Block Lock bits (BL0 and BL1) or the

PPEN bit. RWEL is reset when the Block Lock or

PPEN bits are changed, or when the part powers-up

again.

Programming the BL or PPEN Bits

A three step sequence is required to change the

nonvolatile Block Lock or Program Protect Enable:

1) Set WEL = 1 (write 00000010 to the highest

address location, volatile write cycle)

(Start)

2) Set RWEL = 1 (write 00000110 to the highest

address location, volatile write cycle)

(Start)

3) Set BL1, BL0, and/or PPEN bits (Write w00yz010 to

the highest address location)

w = PPEN, y = BL1, Z = BL0,

(Stop)

Step 3 is a nonvolatile program cycle, requiring 10ms

to complete. RWEL is reset (0) by this program cycle,

requiring another program cycle to set RWEL again

before the Block Lock bits can be changed. RWEL

must be 0 in step 3; if w00yz110 is written to the

highest address location, RWEL is set but PPEN,

BL1 and BL0 are not changed (the device remains at

step 2).