Table A.1: Watchdog timer registers
Address of | Read/Write | Value (2F) & description |
register (2E) |
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87 (hex) | Write this address to I/O address port 2E (hex) twice to | |
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| unlock the W83627HF |
07 (hex) | write | Write 08 (hex) to select register of watchdog timer. |
30 (hex) | write | Write 01 (hex) to enable the function of the watchdog |
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| timer. Disabled is set as default. |
F5 (hex) | write | Set seconds or minutes as units for the timer. Write 0 to |
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| bit 3: set seconds as counting unit. [default]. Write 1 to bit |
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| 3: set minutes as counting unit. |
F6 (hex) | write | 0: stop timer [default] |
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| 01 ~ FF (hex): The amount of the count, in seconds or |
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| minutes, depends on the value set in register F5 (hex). |
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| This number decides how long the watchdog timer waits |
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| for strobe before generating an interrupt or reset signal. |
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| Writing a new value to this register can reset the timer to |
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| count with the new value. |
F7 (hex) | read/write | Bit 6: Write 1 to enable keyboard to reset the timer, 0 to |
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| disable.[default] |
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| Bit 5: Write 1 to generate a timeout signal immediately |
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| and automatically return to 0. [default=0] |
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| Bit 4: Read status of watchdog timer, 1 means timer is |
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| "timeout". |
AA (hex) | Write this address to I/O port 2E (hex) to lock the watch- | |
|
| dog timer 2. |
A.3.1 Example Programs
Enable watchdog timer and set 10 seconds as the timeout interval
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Mov dx,2eh | ; Unlock W83627HF | |
Mov al,87h |
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Out dx,al |
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Out dx,al |
| |
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Mov al,07h | ; Select registers of watchdog timer | |
Out | dx,al |
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Inc | dx |
|
Mov | al,08h |
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Out | dx,al |
|
| ||
Dec dx |
| ; Enable the function of watchdog timer |
Mov | al,30h |
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Out | dx,al |
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Inc | dx |
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Mov | al,01h |
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Out | dx,al |
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92 |
