T89C51CC01 Atmel, T89C51CC01 Datasheet - Page 52

• Manufacturer Part Number: T89C51CC01
• Description: Enhanced 8-Bit Microcontroller
• Manufacturer: Atmel

Boot Process
Software Boot Process
Example
Hardware Boot Process
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T89C51CC01
Many algorithms can be used for the software boot process. Below are descriptions of
the different flags and Bytes.
Boot Loader Jump Bit (BLJB):
- This bit indicates if on RESET the user wants to jump to this application at address
@0000h on FM0 or execute the boot loader at address @F800h on FM1.
- BLJB = 0 (i.e. bootloader FM1 executed after a reset) is the default Atmel factory pro-
gramming.
- To read or modify this bit, the APIs are used.
Boot Vector Address (SBV):
- This byte contains the MSB of the user boot loader address in FM0.
- The default value of SBV is FFh (no user boot loader in FM0).
- To read or modify this byte, the APIs are used.
Extra Byte (EB) and Boot Status Byte (BSB):
- These Bytes are reserved for customer use.
- To read or modify these Bytes, the APIs are used.
At the falling edge of RESET, the bit ENBOOT in AUXR1 register is initialized with the
value of Boot Loader Jump Bit (BLJB).
Further at the falling edge of RESET if the following conditions (called Hardware condi-
tion) are detected. The FCON register is initialized with the value 00h and the PC is
initialized with F800h (FM1 lower byte = Bootloader entry point).
Hardware Conditions:
•
•
•
The Hardware condition forces the bootloader to be executed, whatever BLJB value is.
Then BLBJ will be checked.
If no hardware condition is detected, the FCON register is initialized with the value F0h.
Then BLJB value will be checked.
Conditions are:
•
•
Note:
PSEN low
EA high,
ALE high (or not connected).
If bit BLJB = 1:
User application in FM0 will be started at @0000h (standard reset).
If bit BLJB = 0:
Boot loader will be started at @F800h in FM1.
2. To ensure correct microcontroller startup, the PSEN pin should not be tied to ground
1. As PSEN is an output port in normal operating mode (running user applications or
bootloader applications) after reset it is recommended to release PSEN after the fall-
ing edge of Reset is signaled.
The hardware conditions are sampled at reset signal Falling Edge, thus they can be
released at any time when reset input is low.
during power-on.
(1)
4129K–CAN–01/05