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Functional Description
2.4
Special Board Functions
2.4.1
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 con-
figuration details). The watchdog timing has four possible settings: 0.5, 1.0, 1.5, and 2.0 sec-
onds. 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 reset-
ting 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.
2.4.2
Realtime Clock (STC M41T56)
A separate hardware realtime clock (RTC) is incorporated on the CP321 board which provides
clock information via the I²C bus for application use. An eight byte wide register (refer to chapter
4 for description) is available for accessing, setting, and starting the RTC. The RTC must be
initialized prior to its use whereby settings are possible for seconds, minutes, hours, day, date,
month, year, and calibration information. Continuous clock operation (even with system power
off) is possible through the use of a rechargable Gold Cap, or alternately, lithium battery buff-
ering is possible. Accuracy of the RTC is 35 ppm whereby temperature compensation can be
adjusted in steps of +4.068 or -2.034 ppm per software using the onboard digital temperatur
sensor (LM75).
For calibration purposes the RTC can also generate a 512
Hz test signal which is made available at test jack J2 (figure
1-3 indicates the location of J2 on the board). Please refer
to the datasheet of the ST M41T56 for more information
concerning calibration.
2.4.3
Reset/Abort
On the CP321 front panel there are two push button switches for in-
teracting with the system: RST for reset and AB for abort.
Pressing the RST button initiates an immediate hardware reset of the
system.
During normal operation pressing the AB button causes a non-
maskable interrupt (NMI) to be generated. In addition it is latched into
a bit in the System Logic, the purpose of which is to differentiate be-
tween the NMI initiated from the ABORT Button and the NMI initiated
from the Watchdog Timer.
Pressing the AB button during system startup when the U LED
(green) is blinking causes the bootstrap loader to enter interactive
command mode. Commands can then be entered for processing by
the bootstrap loader. Refer to chapter 5 for Bootstrap Loader infor-
mation.
Page 2 - 16
© 2003 Kontron Modular Computers GmbH
CP321
Figure 2-4: RTC J2 Pinout
1
FT GND
2
FT OUT
Figure 2-5: CP321
CP 321
W
ID 24977, Rev. 02
Front
Panel
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