M50LPW080

22/44

Lock Down. The Lock Down Bit provides a

mechanism for protecting software data from sim-

ple hacking and malicious attack. When the Lock

Down Bit is set, ‘1’, further modification to the

Write Lock, Read Lock and Lock Down Bits cannot

be performed. A reset or power-up is required be-

fore changes to these bits can be made. When the

Lock Down Bit is reset, ‘0’, the Write Lock, Read

Lock and Lock Down Bits can be changed.

General Purpose Input Register

The General Purpose Input Register holds the

state of the General Purpose Input pins, GPI0-

GPI4. When this register is read, the state of these

pins is returned. This register is read-only and writ-

ing to it has no effect.

The signals on the General Purpose Input pins

should remain constant throughout the whole Bus

Read cycle in order to guarantee that the correct

data is read.

Table 13. Lock Register Bit Definitions

Note: Applies to Top Block Lock Register (T_BLOCK_LK) and Top Block [-1] Lock Register (T_MINUS01_LK) to Top Block [-15] Lock Reg-

ister (T_MINUS15_LK).

Table 14. General Purpose Input Register Definition

Note: Applies to the General Purpose Input Register (GPI_REG).

Bit

Bit Name

Value

Function

7-3

Reserved

2

Read-Lock

‘1’

Bus Read operations in this Block always return 00h.

‘0’

Bus read operations in this Block return the Memory Array contents. (Default

value).

1

Lock-Down

‘1’

Changes to the Read-Lock bit and the Write-Lock bit cannot be performed. Once a

‘1’ is written to the Lock-Down bit it cannot be cleared to ‘0’; the bit is always reset

to ‘0’ following a Reset (using RP or INIT) or after power-up.

‘0’

Read-Lock and Write-Lock can be changed by writing new values to them. (Default

value).

0

Write-Lock

‘1’

Program and Block Erase operations in this Block will set an error in the Status

Register. The memory contents will not be changed. (Default value).

‘0’

Program and Block Erase operations in this Block are executed and will modify the

Block contents.

Bit

Bit Name

Value

Function

7-5

Reserved

4GPI4

‘1’

‘0’

3GPI3

‘1’

‘0’

2GPI2

‘1’

‘0’

1GPI1

‘1’

‘0’

0GPI0

‘1’

‘0’