User`s manual

DIGITAL-LOGIC AG MSMP5 / P3 SEN/SEV Manual V1.6A
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4.5.3 External battery assembling:
If customer wants to connect an external battery (check for the appropriate connector in the chapter
DESCRIPTION OF THE CONNECTORS), then some precautions have to be made:
• To prevent, that the external battery gets charged from the board, a diode has to be assembled in serial
from the battery to the connector
This is not necessary anymore since boardversion V3.8 (Schottky- diode included onboard)
• The RTC device (PIIX4) defines a voltage level of 2.0V...3.6V, so do use an external battery, which will
be in this range (inclusive the diode which is already assembled onboard since V3.8)
4.5.4 Watchdog
The watchdog timer detects a system crash and performs a hardware reset. After power up, the watchdog is
always disabled as the BIOS does not send strobes to the watchdog. In case that the user wants to take ad-
vantage of the watchdog, the application must produce a strobe at least every 800 ms. If no strobe occures
within the 800 ms, the watchdog resets the system.
To program the watchdog in user application DIGITAL-LOGIC AG has implemented a special BIOS exten-
sion in interrupt 15h (function: EBh).
Calling this function by setting a 1 in the AL- Register, turns on the watchdog and performs a strobe. Calling
the same function with a 0 in the AL-Register, turns off the watchdog.
The following part has to be implemented in the users application:
Watchdog on: The application has to call interrupt 15h function EBh and set a 1 into the AL-register at least
every 800 ms.
Watchdog off: The application has to call interrupt 15h function EBh and set a 0 into the AL-register
within 800 ms after the last strobe has been sent while the watchdog was still in func-
tion (if the watchdog is not turned off in time, it will reset the system again!).
See also chapter 11