參數(shù)資料
型號(hào)： DS89C420
英文描述： Ultra-High-Speed Microcontroller
中文描述： 超高速微控制器
文件頁(yè)數(shù)： 36/59頁(yè)
文件大?。?/td> 539K
代理商： DS89C420
DS89C420
36 of 59
Timed Access
The timed access function provides control verification to system functions. The timed access function
prevents an errant CPU from making accidental changes to certain SFR bits that are considered vital to
proper system operation. This is achieved by using software control when accessing the following SFR
control bits:
WDCON.0
WDCON.1
WDCON.3
WDCON.6
EXIF.0
ACON.5
ACON.6
ACON.7
ROMSIZE.0
ROMSIZE.1
ROMSIZE.2
ROMSIZE.3
FCNTL.0
FCNTL.1
FCNTL.2
FCNTL.3
RWT
EWT
WDIF
POR
BGS
PAGES0
PAGES1
PAGEE
RMS0
RMS1
RMS2
PRAME
FC0
FC1
FC2
FC3
Reset Watchdog Timer
Watchdog Reset Enable
Watchdog Interrupt Flag
Power-On Reset Flag
Bandgap Select
Page Mode Select Bit 0
Page Mode Select Bit 1
Page Mode Enable
Program Memory Size Select Bit 0
Program Memory Size Select Bit 1
Program Memory Size Select Bit 2
Program RAM Enable
Flash Command Bit 0
Flash Command Bit 1
Flash Command Bit 2
Flash Command Bit 3
Before these bits can be altered, the processor must execute the timed access sequence. This sequence
consists of writing an AAh to the timed access (TA, C7h) register, followed by writing a 55h to the same
register within three machine cycles. This timed sequence of steps then allows any of the timed access-
protected SFR bits to be altered during the three machine cycles, following the writing of the 55h.
Writing to a timed access-protected bit outside of these three machine cycles has no effect on the bit.
The timed access process is address-, data-, and time-dependent. A processor running out of control and
not executing system software cannot statistically perform this timed sequence of steps, and as such, will
not accidentally alter the protected bits. It should be noted that this method should be used in the main
body of the system software and
never
used in an interrupt routine in conjunction with the watchdog
reset. Interrupt routines using the timed-access watchdog-reset bit (RWT) can recover a lost system and
allow the resetting of the watchdog, but the system returns to a lost condition once the RETI is executed,
unless the stack is modified. It is advisable that interrupts be disabled (EA = 0) when executing the timed
access sequence, since an interrupt during the sequence adds time, making the timed access attempt fail.
相關(guān)PDF資料
PDF描述
DS89C420-ECL Ultra-High-Speed Microcontroller
DS89C420-MCL Ultra-High-Speed Microcontroller
DS9094 iButtonTM Clip
DS9097 COM Port Adapter
DS9097E COM Port Adapter
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
DS89C420_02 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:Ultra-High-Speed Microcontroller
DS89C420_05 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:Ultra-High-Speed Microcontroller
DS89C420-ECL 功能描述:IC MCU ULTRA 33MHZ HP 44-TQFP RoHS:否 類別:集成電路 (IC) >> 嵌入式 - 微控制器， 系列:89C 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:260 系列:73S12xx 核心處理器:80515 芯體尺寸:8-位 速度:24MHz 連通性:I²C，智能卡，UART/USART，USB 外圍設(shè)備:LED，POR，WDT 輸入/輸出數(shù):9 程序存儲(chǔ)器容量:64KB（64K x 8） 程序存儲(chǔ)器類型:閃存 EEPROM 大小:- RAM 容量:2K x 8 電壓 - 電源 (Vcc/Vdd):2.7 V ~ 5.5 V 數(shù)據(jù)轉(zhuǎn)換器:- 振蕩器型:內(nèi)部 工作溫度:-40°C ~ 85°C 封裝/外殼:68-VFQFN 裸露焊盤 包裝:管件
DS89C420-ECS 功能描述:IC MCU 50MHZ ULTRA HS 44-TQFP RoHS:否 類別:集成電路 (IC) >> 嵌入式 - 微控制器， 系列:89C 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:260 系列:73S12xx 核心處理器:80515 芯體尺寸:8-位 速度:24MHz 連通性:I²C，智能卡，UART/USART，USB 外圍設(shè)備:LED，POR，WDT 輸入/輸出數(shù):9 程序存儲(chǔ)器容量:64KB（64K x 8） 程序存儲(chǔ)器類型:閃存 EEPROM 大小:- RAM 容量:2K x 8 電壓 - 電源 (Vcc/Vdd):2.7 V ~ 5.5 V 數(shù)據(jù)轉(zhuǎn)換器:- 振蕩器型:內(nèi)部 工作溫度:-40°C ~ 85°C 封裝/外殼:68-VFQFN 裸露焊盤 包裝:管件
DS89C420-ENG 功能描述:IC MCU ULTRA 25MHZ HP 44-TQFP RoHS:否 類別:集成電路 (IC) >> 嵌入式 - 微控制器， 系列:89C 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:260 系列:73S12xx 核心處理器:80515 芯體尺寸:8-位 速度:24MHz 連通性:I²C，智能卡，UART/USART，USB 外圍設(shè)備:LED，POR，WDT 輸入/輸出數(shù):9 程序存儲(chǔ)器容量:64KB（64K x 8） 程序存儲(chǔ)器類型:閃存 EEPROM 大小:- RAM 容量:2K x 8 電壓 - 電源 (Vcc/Vdd):2.7 V ~ 5.5 V 數(shù)據(jù)轉(zhuǎn)換器:- 振蕩器型:內(nèi)部 工作溫度:-40°C ~ 85°C 封裝/外殼:68-VFQFN 裸露焊盤 包裝:管件
發(fā)布緊急采購(gòu)，3分鐘左右您將得到回復(fù)。

采購(gòu)需求

(若只采購(gòu)一條型號(hào)，填寫一行即可)

發(fā)布成功！您可以繼續(xù)發(fā)布采購(gòu)。也可以進(jìn)入我的后臺(tái)，查看報(bào)價(jià)

發(fā)布成功！您可以繼續(xù)發(fā)布采購(gòu)。也可以進(jìn)入我的后臺(tái)，查看報(bào)價(jià)

*型號(hào) *數(shù)量 廠商 批號(hào) 封裝
添加更多采購(gòu)

我的聯(lián)系方式

*
*
*