AT89C51AC2 datasheet(33/121 Pages) ATMEL

33 / 121 page

A/T89C51AC2

4127G–8051–05/06

Program/Code

Memory

The A/T89C51AC2 implement 32 KB of on-chip program/code memory. Figure 17

shows the partitioning of internal and external program/code memory spaces depending

on the product.

The Flash memory increases EPROM and ROM functionality by in-circuit electrical era-

sure and programming. Thanks to the internal charge pump, the high voltage needed for

programming or erasing Flash cells is generated on-chip using the standard VDD volt-

age. Thus, the Flash Memory can be programmed using only one voltage and allows In-

System-Programming commonly known as ISP. Hardware programming mode is also

available using specific programming tool.

Figure 17. Program/Code Memory Organization

Notes:

1. If the program executes exclusively from on-chip code memory (not from external

memory), beware of executing code from the upper byte of on-chip memory (7FFFh)

and thereby disrupt I/O Ports 0 and 2 due to external prefetch. Fetching code con-

stant from this location does not affect Ports 0 and 2.

2. Default factory programmed parts come with maximum hardware protection. Execu-

tion from external memory is not possible unless the Hardware Security Byte is

reprogrammed. See Table 26.

0000h

32 KB

7FFFh

internal

0000h

7FFFh

FFFFh

8000h

Flash

32 KB

external

memory

32 KB

external

memory

EA = 0

EA = 1

AT89C51AC2 Datasheet(PDF) 33 Page - ATMEL Corporation