Datasheet

99
4235K–8051–05/08
AT89C51RD2/ED2
24.6.3 Functional Description
Figure 24-3. Bootloader Functional Description
On the above diagram, the on-chip bootloader processes are:
• ISP Communication Management
The purpose of this process is to manage the communication and its protocol between the on-
chip bootloader and a external device. The on-chip ROM implements a serial protocol (see sec-
tion “Bootloader Protocol”). This process translate serial communication frame (UART) into
Flash memory access (read, write, erase, etc.).
• User Call Management
Several Application Program Interface (API) calls are available for use by an application pro-
gram to permit selective erasing and programming of Flash pages. All calls are made through a
common interface (API calls), included in the ROM bootloader. The programming functions are
selected by setting up the microcontroller’s registers before making a call to a common entry
point (0xFFF0). Results are returned in the registers. The purpose on this process is to translate
the registers values into internal Flash Memory Management.
• Flash Memory Management
This process manages low level access to Flash memory (performs read and write access).
ISP Communication
Management
User
Application
Specific Protocol
Communication
Management
Flash
Memory
External Host with
Flash Memory
User Call
Management (API)