Kontron VMP2 - Manual (Page 46)

VMP2 Functional Description
ID 24855, Rev. 02 Page 2 - 18 © 2002 PEP Modular Computers GmbH
2.6 Special Board Features
2.6.1 Watchdog Timer
A watchdog timer is available which (when enabled) on timeout forces either a non-
maskable interrupt (NMI) to be generated or causes a system reset to occur (refer to
chapter 4 for configuration details). It is also possible to generate, as a first step, an NMI
and then, as a second step, a system reset (in Cascade mode).The watchdog timing
has four possible settings: 0.5, 1.0, 1.5, and 2.0 seconds. After selecting the timeout
value and routing (NMI or reset) the watchdog can be enabled. Once enabled, the
watchdog must be continuously retriggered or a timeout will occur. When the watchdog
timer is enabled, it cannot be stopped or reprogrammed except by resetting the system.
The yellow watchdog LED (W) indicates the enabling status of the watchdog. Prior to
the watchdog being enabled it is off. After enabling it comes on and remains on until a
system reset occurs.
2.6.2 RTC (STC M41T56)
The Real Time Clock provides the following features:
• counters for seconds, minutes, hours, day, date, month and year.
• clock calibration by software
• low supply current for buffering with Gold Caps
• alternatively a battery may be placed on the board to buffer the RTC for a longer
time
• it is also possible to buffer the power supply for the RTC via the VME-5V-Standby
power line
• automatic leap year compensation
• precision: 35 ppm
• for greater precision or for temperature compensation the RTC can be adjusted in
in steps of +4.068 or –2.034 ppm
• for temperature compensation, the onboard temperature sensor (LM75) may be
used
2.6.3 Reset/Abort
There are also 2 push button switches with the function ABORT and RESET. The
RESET button reinitializes the board via hardware.
The ABORT button initiates the NMI. In addition it is latched into a bit in the System
Logic, the purpose of this is to differentiate between the NMI initiated from the ABORT
Button and the NMI initiated from the watchdog.
The positions of the Abort and Reset
buttons on the Front Panel may be viewed in Figure 2-2.