AT83SND1CXXX-ROTIL datasheet(20/212 Pages) ATMEL

20 / 212 page

4109J–8051–10/06

AT8xC51SND1C

Figure 6-6.

AT89C51SND1C Memory Architecture

6.3.1

User Space

This space is composed of a 64K Bytes Flash memory organized in 512 pages of 128 Bytes. It

contains the user’s application code.

This space can be read or written by both software and hardware modes.

6.3.2

Boot Space

This space is composed of a 4K Bytes Flash memory. It contains the boot loader for In-System

Programming and the routines for In Application Programming.

This space can only be read or written by hardware mode using a parallel programming tool.

6.3.3

Hardware Security Space

This space is composed of one Byte: the Hardware Security Byte (HSB see Table 23) divided in

2 separate nibbles. The MSN contains the X2 mode configuration bit and the Boot Loader Jump

Bit as detailed in Section “Boot Memory Execution”, page 5 and can be written by software while

the LSN contains the lock system level to protect the memory content against piracy as detailed

in Section “Hardware Security System”, page 4 and can only be written by hardware.

6.3.4

Extra Row Space

This space is composed of 2 Bytes:

•

The Software Boot Vector (SBV, see Table 24).

This Byte is used by the software boot loader to build the boot address.

•

The Software Security Byte (SSB, see Table 25).

This Byte is used to lock the execution of some boot loader commands.

6.4

Hardware Security System

The AT89C51SND1C implements three lock bits LB2:0 in the LSN of HSB (see Table 23) pro-

viding three levels of security for user’s program as described in Table 23 while the AT83SND1C

is always set in read disabled mode.

Level 0 is the level of an erased part and does not enable any security feature.

Level 1 locks the hardware programming of both user and boot memories.

FFFFh

64K Bytes

Flash Memory

0000h

Hardware Security

User

4K Bytes

Flash Memory

FFFFh

F000h

Boot

Extra Row

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