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SECTION 3 - MICROBOARD 031-01730-000
Flash memory cards are revised to add new features,
enhancements and program corrections. Each time
they are revised, the revision level of the affected por-
tion of the program (controls or language) increments.
Each time they are revised, a Service Information Bul-
letin is issued that describes the new features. Those
bulletins that have been issued to date are located at the
rear of this manual.
The microprocessor controls the chiller by reading and
executing the Program instructions in a sequence de-
termined by the Program. Under Program control, the
microprocessor reads the Analog and Digital inputs to
determine the operating conditions and controls Digi-
tal Outputs based upon these inputs. These inputs are
compared to stored thresholds to determine if a Safety
or Cycling shutdown is required. If a threshold has
been exceeded, a shutdown is performed and the ap-
propriate message is retrieved from the Program and
displayed on the Liquid Crystal Display.
As operating conditions require, status messages are
retrieved and displayed. The keypad is read as Digi-
tal inputs, when an operator presses a key to request a
display; the microprocessor interprets the request, re-
trieves the display from the Program and displays it.
The Program assembles data in the correct format for
transmission through the serial data ports to peripheral
devices. The Program also instructs the microproces-
sor to respond to requests from peripheral devices for
serial data transmissions.
The Watchdog circuit monitors the +5 VDC supply
from the external Power Supply to determine when a
power failure is occurring. Just before the supply de-
creasing to a level where the microprocessor and sup-
porting circuits can no longer operate, it applies a reset
signal to the microprocessor.
The microprocessor responds by de-energizing the
run digital output through the FPGA, shutting down
the chiller and retrieving the POWER FAILURE mes-
sage from the Program and sending it to the Display
Controller for display. Similarly, when power is first
applied after a power failure, it maintains the micro-
processor in a reset state until the +5 VDC has returned
to a sufficient level.
The watchdog circuit also ensures that all the program
instructions are being performed and that the Program
has not latched-up, bypassing important safety thresh-
olds. If the Program has latched-up, the microproces-
sor initiates a safety shutdown and displays WATCH-
DOG – SOFTWARE REBOOT message.
32
The BIOS EPROM (basic input/output system erasable
programmable read only memory) is a memory device
that contains the bootstrap or power-up program. It is
located in socket location U45. This EPROM is replace-
able. Refer to YORK Renewal Parts - OptiView Control
Center (Form 160.54-RP1). The EPROM version is an
alpha-numeric code that represents the application and
revision level. The version is printed on a label adhered
to the EPROM's surface. The version code is as follows:
C. MLM.
Early vintage chillers were equipped with BIOS EPROM
(P/N 031-01796-001). It is no longer used and was su-
perseded by BIOS EPROM (P/N 031-01796-002).
When power is applied to the OptiView Control Center
following a power failure, the microprocessor executes
the instructions in the BIOS EPROM program to ini-
tialize, configure and start operation of certain mi-
croboard components before the main program (stored
in the flash memory card) is started.
Depending upon the application, the microboard could
be equipped with an EPROM with 128K, 256K or
512K capacity. Microboard Program Jumper JP38
must be positioned according to the actual EPROM in-
stalled. See Program Jumpers on page 42.
JCI COMPANY CONFIDENTIAL
ISSUE DATE: 10/25/2019
00. XX.
Revision level. Increments 01, 02 etc.
YK Chiller BIOS EPROM
IMPORTANT! EPROM (P/N 031-01796-
002) is not compatible with all versions
of flash memory cards. Refer to Service
Replacement on page 38 for more in-
formation.
JOHNSON CONTROLS
FORM 160.54-M1
Centrifugal Chiller
Commercial Chiller
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