AT89C51AC3-RDTIM datasheet(40/143 Pages) ATMEL

40 / 143 page

AT89C51AC3

4383B–8051–01/05

Figure 22. External Code Fetch Waveforms

Flash Memory

Architecture

AT89C51AC3 features two on-chip Flash memories:

•

Flash memory FM0:

containing 64K Bytes of program memory (user space) organized into 128 byte

pages,

•

Flash memory FM1:

2K Bytes for boot loader and Application Programming Interfaces (API).

The FM0 can be program by both parallel programming and Serial In-System Program-

ming (ISP) whereas FM1 supports only parallel programming by programmers. The ISP

mode is detailed in the "In-System Programming" section.

All Read/Write access operations on Flash Memory by user application are managed by

a set of API described in the "In-System Programming" section.

The bit ENBOOT in AUXR1 register is used to map FM1 from F800h to FFFFh. Figure

23 and Figure 24 show the Flash memory configuration with ENBOOT=1 and

ENBOOT=0.

Figure 23. Flash Memory Architecture with ENBOOT=1 (boot mode)

ALE

PSEN#

PCL

PCH

PCL

D7:0

PCH

D7:0

CPU Clock

FFFFh

64K Bytes

FM0

0000h

Hardware Security (1 byte)

Column Latches (128 Bytes)

Extra Row (128 Bytes)

2K Bytes

Flash memory

FM1

boot space

FFFFh

F800h

FM1 mapped between FFFFh and

F800h when bit ENBOOT is set in

AUXR1 register

F800h

Memory space not accessible

AT89C51AC3-RDTIM Datasheet(PDF) 40 Page - ATMEL Corporation

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