AT8xC51SND2C
Program/Code
Memory
The AT8xC51SND2C execute up to 64K Bytes of program/code memory. Figure 9
shows the split of internal and external program/code memory spaces depending on the
product.
The AT83SND2C product provides the internal program/code memory in ROM memory
while the AT89C51SND2C product provides it in Flash memory. These 2 products do
not allow external code memory execution.
The Flash memory increases EPROM and ROM functionality by in-circuit electrical era-
sure and programming. The high voltage needed for programming or erasing Flash cells
is generated on-chip using the standard VDD voltage, made possible by the internal
charge pump. Thus, the AT89C51SND2C can be programmed using only one voltage
and allows In-application software programming. Hardware programming mode is also
available using common programming tools. See the application note ‘Programming
T89C51x and AT89C51x with Device Programmers’.
The AT89C51SND2C implements an additional 4K Bytes of on-chip boot Flash memory
provided in Flash memory. This boot memory is delivered programmed with a standard
boot loader software allowing In-System Programming (ISP). It also contains some
Application Programming Interface routines named API routines allowing In Application
Programming (IAP) by using user’s own boot loader.
Figure 9. Program/Code Memory Organization
FFFFh
FFFFh
F000h
FFFFh
F000h
4K Bytes
Boot Flash
64K Bytes
Code ROM
64K Bytes
Code Flash
0000h
0000h
AT83SND2C
AT89C51SND2C
ROM Memory
Architecture
As shown in Figure 10 the AT83SND2C ROM memory is composed of one space
detailed in the following paragraph.
Figure 10. AT83SND2C Memory Architecture
FFFFh
64K Bytes
User
ROM Memory
0000h
17
4341D–MP3–04/05
ATMEL [ ATMEL ]
