User`s manual

DIGITAL-LOGIC AG MSLB-P5 Manual V0.3
PRELIMINARY 44
4.5.2 Battery backed clock (RTC)
An AT compatible date/time clock is located within the chipset. 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 DIGITAL-LOGIC replacement part: PCC-P5L 3V-BAT. The battery-backed clock can be
set by using the DIGITAL-LOGIC AG SETUP at boot-time.
Addresses: 70h = Index register
71h = Data transfer register
RTC-Address MAP: 00 - 0F RTC (Real time clock)
10 - 3F BIOS setup (Standard)
40 - 7F Extended BIOS or SuperState BIOS setup
The chipset consumes the following currents:
Typical battery current at 25°C : 0.2 µA Lifetime around 10 years at 25°C
4.5.3 Watchdog
The watchdog timer detects a system crash and performs a hardware reset. After powering-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 applications 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 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!).