參數(shù)資料
型號(hào)： AT89C51AC2-SLSUM
廠商： Atmel
文件頁數(shù)： 65/121頁
文件大?。?/td> 0K
描述： IC 8051 MCU FLASH 32K 44PLCC
產(chǎn)品培訓(xùn)模塊： MCU Product Line Introduction
標(biāo)準(zhǔn)包裝： 972
系列： 89C
核心處理器： 8051
芯體尺寸： 8-位
速度： 40MHz
連通性： UART/USART
外圍設(shè)備： POR，PWM，WDT
輸入/輸出數(shù)： 34
程序存儲(chǔ)器容量： 32KB（32K x 8）
程序存儲(chǔ)器類型： 閃存
EEPROM 大?。?/td> 2K x 8
RAM 容量： 1.25K x 8
電壓 - 電源 (Vcc/Vdd)： 3 V ~ 5.5 V
數(shù)據(jù)轉(zhuǎn)換器： A/D 8x10b
振蕩器型： 外部
工作溫度： -40°C ~ 85°C
封裝/外殼： 44-LCC（J 形引線）
包裝： 管件
48
A/T89C51AC2
4127H–8051–02/08
Boot Process
Software Boot Process
Example
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 FCh (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.
Hardware Boot Process
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).
Harware Conditions:
PSEN low(1)
EA high,
ALE high (or not connected).
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:
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.
Note:
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.
2. To ensure correct microcontroller startup, the PSEN pin should not be tied to ground
during power-on.
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