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參數資料
| 型號： | W79E201 |
| 廠商： | WINBOND ELECTRONICS CORP |
| 元件分類： | 8位微控制器 |
| 英文描述： | 8-BIT MICROCONTROLLER |
| 中文描述： | 8位微控制器 |
| 文件頁數： | 63/87頁 |
| 文件大小： | 818K |
| 代理商： | W79E201 |
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W79E201
Publication Release Date: December 16, 2004
- 63 -
Revision A2
16. TIMED ACCESS PROTECTION
The W79E201 has several new features, like the Watchdog timer, on-chip ROM size adjustment, wait
state control signal and Power on/fail reset flag, which are crucial to proper operation of the system. If
left unprotected, errant code may write to the Watchdog control bits resulting in incorrect operation
and loss of control. In order to prevent this, the W79E201 has a protection scheme which controls the
write access to critical bits. This protection scheme is done using a timed access.
In this method, the bits which are to be protected have a timed write enable window. A write is
successful only if this window is active, otherwise the write will be discarded. This write enable window
is open for 3 machine cycles if certain conditions are met. After 3 machine cycles, this window
automatically closes. The window is opened by writing AAh and immediately 55h to the Timed Access
(TA) SFR. This SFR is located at address C7h. The suggested code for opening the timed access
window is
TA
REG
0C7h
; Define new register TA, located at 0C7h
MOV
TA, #0AAh
MOV
TA, #055h
When the software writes AAh to the TA SFR, a counter is started. This counter waits for 3 machine
cycles looking for a write of 55h to TA. If the second write (55h) occurs within 3 machine cycles of the
first write (AAh), then the timed access window is opened. It remains open for 3 machine cycles,
during which the user may write to the protected bits. Once the window closes the procedure must be
repeated to access the other protected bits.
Examples of Timed Assessing are shown below.
Example 1: Valid access
MOV
TA, #0AAh
3 M/C ; Note: M/C = Machine Cycles
MOV
TA, #055h
3 M/C
MOV
WDCON, #00h
3 M/C
Example 2: Valid access
MOV
TA, #0AAh
3 M/C
MOV
TA, #055h
3 M/C
NOP
1 M/C
SETB EWT
2 M/C
Example 3: Valid access
MOV
TA, #0Aah
3 M/C
MOV
TA, #055h
3 M/C
ORL
WDCON, #00000010B 3M/C
Example 4: Invalid access
MOV
TA, #0AAh
3 M/C
MOV
TA, #055h
3 M/C
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相關代理商/技術參數 |
參數描述 |
|---|---|
| W79E201A16FL | 功能描述:IC MCU 8-BIT 16K FLASH 44-PQFP RoHS:是 類別:集成電路 (IC) >> 嵌入式 - 微控制器， 系列:W79 標準包裝:300 系列:78K0R/Ix3 核心處理器:78K/0R 芯體尺寸:16-位 速度:40MHz 連通性:3 線 SIO，I²C，LIN，UART/USART 外圍設備:DMA，LVD，POR，PWM，WDT 輸入/輸出數:27 程序存儲器容量:16KB（16K x 8） 程序存儲器類型:閃存 EEPROM 大小:- RAM 容量:1K x 8 電壓 - 電源 (Vcc/Vdd):2.7 V ~ 5.5 V 數據轉換器:A/D 8x10b 振蕩器型:內部 工作溫度:-40°C ~ 85°C 封裝/外殼:38-SSOP 包裝:托盤 |
| W79E201A16FN | 制造商:WINBOND 制造商全稱:Winbond 功能描述:8-BIT MICROCONTROLLER |
| W79E201A16LN | 制造商:WINBOND 制造商全稱:Winbond 功能描述:8-BIT MICROCONTROLLER |
| W79E201A16PL | 功能描述:IC MCU 8-BIT 16K FLASH 44-PLCC RoHS:是 類別:集成電路 (IC) >> 嵌入式 - 微控制器， 系列:W79 標準包裝:300 系列:78K0R/Ix3 核心處理器:78K/0R 芯體尺寸:16-位 速度:40MHz 連通性:3 線 SIO，I²C，LIN，UART/USART 外圍設備:DMA，LVD，POR，PWM，WDT 輸入/輸出數:27 程序存儲器容量:16KB（16K x 8） 程序存儲器類型:閃存 EEPROM 大小:- RAM 容量:1K x 8 電壓 - 電源 (Vcc/Vdd):2.7 V ~ 5.5 V 數據轉換器:A/D 8x10b 振蕩器型:內部 工作溫度:-40°C ~ 85°C 封裝/外殼:38-SSOP 包裝:托盤 |
| W79E201A16PN | 制造商:WINBOND 制造商全稱:Winbond 功能描述:8-BIT MICROCONTROLLER |
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