X25097

4

IDLock Operation

Prior to any attempt to perform an IDLock Operation, the

WREN instruction must first be issued. This instruction

sets the “Write Enable” latch and allows the part to

respond to an IDLock sequence (Figure 7). The IDLock

instruction follows and consists of one command byte fol-

lowed by one IDLock byte (See Figure 1). This byte con-

tains the IDLock bits IDL2-IDL0. The rest of the bits [7:3]

are unused and must be written as zeroes. Bringing CS

HIGH after the two byte IDLock instruction initiates a

nonvolatile write to the Status Register. Writing more

than one byte to the Status Register will overwrite the

previously written IDLock byte. See Table 1.

Operational Notes

The X25097 powers up in the following state:

• The device is in the low power, standby state.

• A HIGH to LOW transition on CS is required to enter

an active state and receive an instruction.

• SO pin is at high impedance.

• The “Write Enable” latch is reset.

Data Protection

The following circuitry has been included to prevent inad-

vertant writes:

• The “Write Enable” latch is reset upon power-up.

• A WREN instruction must be issued to set the “Write

Enable” latch.

• CS must come HIGH at the proper clock count in order

to start a write cycle.

Table 1. Instruction Set and Block Lock Protection Byte Definition

7038 FRM T03

*Instructions are shown with MSB in leftmost position. Instructions are transferred MSB first.

Instruction Format*

Instruction Name and Operation

0000 0110

WREN: Set the Write Enable Latch (Write Enable Operation)

0000 0100

WRDI: Reset the Write Enable Latch (Write Disable Operation)

0000 0001

IDLock Instruction—followed by:

IDLock Byte: (See Figure 1)

0000 0000 --->NO IDLock: 00h-00h - - - - - - - - - - - >None of the Array

0000 0001 --->IDLock Q1: 0000h-00FFh - - - - - - - >Lower Quadrant (Q1)

0000 0010 --->IDLock Q2: 0100h-01FFh - - - - - - - >Q2

0000 0011 --->IDLock Q3: 0200h-02FFh - - - - - - - >Q3

0000 0100 --->IDLock Q4: 0300h-03FFh - - - - - - - >Upper Quadrant (Q4)

0000 0101 --->IDLock H1: 0000h-01FFh - - - - - - - >Lower Half of the Array (H1)

0000 0110 --->IDLock P0: 0000h-000Fh - - - - - - - >Lower Page (P0)

0000 0111 --->IDLock Pn: 03F0h-03FFh - - - - - - - >Upper Page (Pn)

0000 0101

READ STATUS: Reads IDLock & write in progress status on SO Pin

0000 0010

WRITE: Write operation followed by address and data

0000 0011

READ: Read operation followed by address