AT89C51RC2-3CSCM データシートの表示（PDF） - Atmel Corporation

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AT89C51RC2-3CSCM

8-bit Microcontroller with 16K/32K Bytes Flash

Atmel Corporation 

Table 69. Program Lock Bits of the SSB

Program Lock Bits

Security

level

LB0 LB1 Protection Description

1

U

U No program lock features enabled.

2

P

U ISP programming of the Flash is disabled.

3

X

P Same as 2, also verify through ISP programming interface is disabled.

Note:

U: unprogrammed or "one" level.

P: programmed or "zero" level.

X: don’t care

WARNING: Security level 2 and 3 should only be programmed after Flash and code

verification.

Flash Memory Status

AT89C51RB2/RC2 parts are delivered in standard with the ISP boot in the Flash mem-

ory. After ISP or parallel programming, the possible contents of the Flash memory are

summarized on Figure 35.

Figure 35. Flash Memory Possible Contents

7FFFh T89C51RC2 32KB

3FFFh T89C51RB2 16KB

Virgin

Application

Virgin

or

Application

Application

Virgin

or

Application

0000h

Default

Memory Organization

After ISP

Dedicated

ISP

After ISP

Dedicated

ISP

After Parallel After Parallel

Programming Programming

In the AT89C51RB2/RC2, the lowest 16K or 32K of the 64 KB program memory address

space is filled by internal Flash.

When the EA pin is high, the processor fetches instructions from internal program Flash.

Bus expansion for accessing program memory from 16K or 32K upward automatic since

external instruction fetches occur automatically when the program counter exceeds

3FFFh (16K) or 7FFFh (32K). If the EA pin is tied low, all program memory fetches are

from external memory.

90 AT89C51RB2/RC2

4180E–8051–10/06

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