Battery Backed Clock (Rtc); Watchdog - DIGITAL-LOGIC MICROSPACE PCC-P5 Technical User's Manual

Table of Contents

DIGITAL-LOGIC AG

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 r e-

placement when the battery is exhausted.

The battery is Digital-Logic replacement part: PCC-P5 3V-BAT. The battery-backed clock can be set by us-

ing the DIGITAL-LOGIC AG SETUP at boot-time.

Addresses:

RTC-Address MAP:

The chipset consumes the following currents:

Typical battery current at 25°C :

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 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 applications DIGITAL-LOGIC AG has implemented a special BIOS exten-

sion 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 function (if the

watchdog is not turned off in time, it will reset the system again!).