AT89C5131-RDTIL datasheet(45/176 Pages) ATMEL

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AT89C5131

4136B–USB–09/03

Hardware Security Byte

Default value after erasing chip: FFh

Notes:

1. Only the 4 MSB bits can be access by software.

2. The 4 LSB bits can only be access by parallel mode.

Table 44. Hardware Security Byte

765

43210

X2B

BLJB

OSCON1

OSCON0

LB2

LB1

LB0

Bit Number

Bit

Mnemonic

Description

7X2B

X2 Bit

Set this bit to start in standard mode

Clear this bit to start in X2 mode.

6BLJB

Bootloader Jump Bit

Set this bit to start the user’s application on next reset at address 0000h.

Cleared this bit to start the bootloader at address F400h (default).

5-4

OSCON1-0

Oscillator Control Bits

These two bits are used to control the oscillator in order to reduce

consumption.

OSCON1

OSCON0 Description

oscillator is configured to run from 0 to 32 MHz

oscillator is configured to run from 0 to 16 MHz

oscillator is configured to run from 0 to 8 MHz

this configuration shouldn’t be set

Reserved

The value read from this bit is indeterminate.

2-0

LB2:0

Lock Bits

AT89C5131-RDTIL Datasheet(PDF) 45 Page - ATMEL Corporation

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