5 hardware security byte – Rainbow Electronics T89C51AC2 User Manual

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T89C51AC2

Rev. B – 19-Dec-01

10.5 Hardware Security
Byte

Table 14. Hardware Security byte

Default value after erasing chip: FFh

Note:

Only the 4 MSB bits can be accessed by software.

Note:

The 4 LSB bits can only be accessed by parallel mode.

X2B

BLJB

LB2

LB1

LB0

Bit

Number

Bit

Mnemonic

Description

X2B

X2 Bit
Set this bit to start in standard mode
Clear this bit to start in X2 mode.

BLJB

Boot Loader JumpBit
- 1: To start the user’s application on next RESET (@0000h) located in FM0,
- 0: To start the boot loader(@F800h) located in FM1.

5-3

Reserved
The value read from these bits are indeterminate.

2-0

LB2:0

Lock Bits