參數(shù)資料
型號: T89C51RD2-3CSIL
廠商: ATMEL CORP
元件分類: 微控制器/微處理器
英文描述: 0 to 40 MHz Flash Programmable 8-bit Microcontroller
中文描述: 8-BIT, FLASH, 25 MHz, MICROCONTROLLER, PDIP40
封裝: PLASTIC, DIP-40
文件頁數(shù): 61/104頁
文件大?。?/td> 798K
代理商: T89C51RD2-3CSIL
61
T89C51RD2
4243G
8051
05/03
Bootloader Functionality
Introduction
The bootloader can be activated by two means: Hardware conditions or regular boot
process.
The Hardware conditions (EA = 1, PSEN = 0) during the Reset# falling edge force the
on-chip bootloader execution. This allows an application to be built that will normally
execute the end user
s code but can be manually forced into default ISP operation.
As PSEN is an output port in normal operating mode (running user application or boor-
loader code) after reset, it is recommended to release PSEN after falling edge of reset
signal. The hardware conditions are sampled at reset signal falling edge, thus they can
be released at any time when reset input is low.
The on-chip bootloader boot process is shown in Figure 24.
Purpose
Hardware Conditions
The Hardware Conditions force the bootloader execution whatever BLJB, BSB
and SBV values.
BLJB
The Boot Loader Jump Bit forces the application execution.
BLJB = 0 => Boot loader execution.
BLJB = 1 => Application execution.
The BLJB is a fuse bit in the Hardware Byte.
That can be modified by hardware (programmer) or by software (API).
Note:
The BLJB test is perform by hardware to prevent any program execution.
SBV
The Software Boot Vector contains the high address of custumer bootloader
stored in the application.
SBV = FCh (default value) if no custumer bootloader in user Flash.
Note:
The custumer bootloader is called by LJMP [SBV]00h instruction.
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