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DS21146D-page 6

Preliminary

© 1996 Microchip Technology Inc.

TABLE 2-1:

INSTRUCTION SET

TABLE 2-2:

WRITE PROTECT FUNCTIONALITY MATRIX

FIGURE 2-1:

WRITE TO STATUS REGISTER AND/OR ARRAY FLOWCHART

Instruction Name

Instruction Format

Description

WREN

0000 0110

Set the write enable latch (enable write operations)

WRDI

0000 0100

Reset the write enable latch (disable write operations)

RDSR

0000 0101

Read status register

WRSR

0000 0001

Write status register (write protect enable and block write protection bits)

READ

0000 0011

Read data from memory array beginning at selected address

WRITE

0000 0010

Write data to memory array beginning at selected address

WPEN

WP

WEL

Protected Blocks

Unprotected Blocks

Status Register

0

X

0

Protected

Protected

Protected

0

X

1

Protected

Writable

Writable

1

Low

0

Protected

Protected

Protected

1

Low

1

Protected

Writable

Protected

X

High

0

Protected

Protected

Protected

X

High

1

Protected

Writable

Writable

CS Returns High

Continue

WEL = 1?

WEL = 1?

WP is low?

WPEN = 1?

Write

Write to

Status Register

Do not write to

Status Register

Write to the

Unprotected Block

Do not write to

Array

No

No

No

No

Yes

Yes

Yes

Yes

No

Yes

No

Yes

To other

Commands

From other

Commands

Write

to Status

Reg?

to array?