York YK-EP Operation And Maintenance Manual page 242

Program Download Connector J26
The SD Program card is inserted into connector J26 to download a program. Refer to instructions
under Service Replacement.
FeRAM
The FeRAM (Ferroelectric Ramdom Access Memory) preserves the stored data during power
failures. All of the programmed Setpoints, Sales Order Data and History Data is stored here. This
memory does not require a battery.
Real Time Clock
The RTC (Real Time Clock) uses a common CR2032 button-cell lithium battery to maintain the time
and date during power outages. The battery life is over 10 years. This type of battery is used in
watches and is readily available at drug stores and appliance stores.
SMARC Module
The SMARC Module is the processor card for the 031-03630-007 microboard. The SMARC Module
and the baseboard are assembled as a pair in the board manufacturing factory and can not be
swapped in the field. SMARC (Smart Mobility ARChitecture) is a relatively new standard to enable
multiple vendors to provide high performance embedded processor cards. This will allow using
future processors if the current ones become obsolete without having to re-design the microboard.
Watchdog Circuit
The Watchdog circuit performs two functions as follows:
• Power failure detection
• Program latch-up detection/prevention
The Watchdog Circuit monitors the +5VDC from the power supply and the +3.3VDC from the
onboard regulator to determine when a power failure is occurring. If the +5VDC decreases to
the threshold of (+4.44VDC to +4.68VDC) or the +3.3VDC decreases to the threshold of (+2.84VDC
to +3.04VDC), a reset is issued to the microprocessor and the chiller shuts down. When power is
restored, the white screen is displayed and the boot-up is performed as described above. When the
graphic screen is displayed, the message CONTROL PANEL – POWER FAILURE is displayed.
The Watchdog Circuit also assures that the entire program is being executed and that the program
has not latched-up, bypassing important safety checks. The Watchdog circuit is a timer that times-
out if not given a reset pulse within its time-out period (1 to 1.204 seconds).
242 YK-EP Style B Centrifugal Chiller