Battery Backed Clock (Rtc); Watchdog - DIGITAL-LOGIC MICROSPACE PC/104 Technical User's Manual

DIGITAL-LOGIC AG
4.5.2

Battery backed clock (RTC)

An AT compatible date/time clock is located within the chips-set. The device also contains a CMOS
static RAM, compatible with that in standard ATs. System configuration data is normally stored in the
clock chip's CMOS RAM in a manner consistent with the convention used in other AT compatible
computers.
One unique feature of the board's battery-backed clock device is that it contains the backup battery
directly on the board. The battery is rated for a minimum of 6 years of clock and internal CMOS RAM
backup under conditions of no power to the board. The battery is removable for easy exchange with a
new type or replacement when the battery is exhausted.
The battery is a DIGITAL-LOGIC AG replacement part: Li 3V-BAT. The battery-backed clock can be
set using the DIGITAL-LOGIC AG SETUP at boot-time.
Addresses:
RTC-Address MAP:
The onboard lithium Battery with 220mAh capacity is able to work over 8 years without replacement.
The chip set consumes the following currents:
Typical battery current at 25°C :
4.5.3

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 the user
wants to take advantage 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
extension in Interrupt 60h (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 60h function EBh and set a 1 into the AL-register
at least every 800 ms.
Watchdog off: The application has to call interrupt 60h 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!).
70h = Index register
71h = Data transfer register
00 - 0F Real time clock
10 - 3F BIOS setup (Standard)
40 - 7F Extended BIOS or SuperState BIOS setup
0,1 µA max. 0,3 µA
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MSM486V Manual V3.22