Portwell PEB-2772VGATM, Руководство пользователя

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System Installation
PEB-2772AVGATM User’s Manual 3-5
3.5 WDT Function
The working algorithm of the WDT function can be simply described as a counting
process. The Time-Out Interval can be set through software programming. The
availability of the time-out interval settings by software or hardware varies from
boards to boards.
PEB-2772VGATM allows users control WDT through dynamic software
programming. The WDT starts counting when it is activated. It sends out a signal to
system reset or to non-maskable interrupt (NMI), when time-out interval ends. To
prevent the time-out interval from running out, a re-trigger signal will need to be sent
before the counting reaches its end. This action will restart the counting process. A
well-written WDT program should keep the counting process running under normal
condition. WDT should never generate a system reset or NMI signal unless the
system runs into troubles.
The related Control Registers of WDT are all included in the following sample
program that is written in C language. User can fill a non-zero value into the
Time-out Value Register to enable/refresh WDT. System will be reset after the
Time-out Value to be counted down to zero. Or user can directly fill a zero value into
Time-out Value Register to disable WDT immediately. To ensure a successful
accessing to the content of desired Control Register, the sequence of following
program codes should be step-by-step run again when each register is accessed.
Additionally, there are maximum 2 seconds of counting tolerance that should be
considered into user’ application program. For more information about WDT, please
refer to Winbond W83627UHG data sheet.
There are 7 PNP I/O port addresses that can be used to configure WDT,
1) 0x2E:EFER (Extended Function Enable Register, for identifying CR index number)
2) 0x07:DEVICE_NUM_REG (Logic Device Number Register)
3) 0x2d:WDT_PIN_SEL_REG (Multi-function Pin Selection Register for WDT )
4) 0x08: WDT_LOGIC_NUM (Logic device number for WDT)
5) 0xf5:WDT_CNT_REG (WDT Control Mode Register. Using for setting time unit.)
6) 0xf6:WDT_COUNT_REG (WDTO# Counter Register. Using for setting the time.)
7) 0xf7:WDT_CS_REG (WDTO# Control & Status Register.)
Below are some example codes, which demonstrate the use of WDT.
//Enter the Extended Function Mode
outp(EFER,
0x87);
outp(EFER, 0x87);
//Enable WDT function