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FORM 160.54-M1
ISSUE DATE: 10/25/2019
Keypad Interface
The keypad is read via J18. The keypad is a matrix of
conductors arranged in rows and columns (See Figure
50 on page 124 and Figure 51 on page 125). There
are 4 rows and 8 columns. When a key is pressed, the
conductors are pressed together at that point, creating
continuity between the row conductor and the column
conductor. The keypad is read by applying a logic low
to a row while leaving +5 VDC pull-up on all other
rows. The microprocessor then reads the 8 columns. If
any column has a logic low on it, the key correspond-
ing to that coordinate (row, column) is being pressed.
The microprocessor reads the entire keypad by repeat-
ing this routine beginning with row 1 and ending with
row 4. The entire keypad is continually read while the
Control Center is powered. See SECTION 10 - KEY-
PAD of this manual for details of the keypad.
CM-2 Board or Style A Solid State Starter
Interface
The microboard retrieves certain operating parameters
(via J10) from the compressor motor starter control
board (CM-2 Current Board for Electromechanical
Starter or Style A Solid State Starter Logic Board).
See the appropriate section of this manual for detailed
explanation of each board. Both boards contain an 8
channel multiplexer. The microprocessor sequentially
and continually reads channels 0 through 7. It reads
each channel by applying a 3-bit binary address to the
TABLE 5 - MULTIPLEXER CHANNELS
0
CM-2
GND
Starter model/
STYLE A
SOLID STATE
voltmeter
STARTER
range
JOHNSON CONTROLS
1
2
3
GND
GND
GND
Current
Phase C
Phase B
limit
motor
motor
command
current
current
JCI COMPANY CONFIDENTIAL
SECTION 4 - MICROBOARD 031-02430-000 AND 031-02430-001
multiplexer. A 0 to 5 VDC analog value is returned
from each channel. The function of each is in the table
below.
The microprocessor determines which board, and
therefore which starter is present, by the value re-
turned from channel 0. Since channels 0 through 6 are
grounded, the CM-2 board returns a 0 VDC value. The
Solid State Starter Logic Board returns a value greater
than 0.41 VDC to +5 VDC. If the value is less than 0.4
VDC, it indicates the starter is an Electromechanical
(EM) starter and the microprocessor then reads chan-
nel 7 to retrieve the peak motor current value. A value
greater than 0.4 VDC indicates the starter is an A style
Solid State Starter and the microprocessor reads chan-
nels 1 through 7.
In the Solid State Starter, channel 0 indicates the start-
er size (model) and voltmeter range (300 VAC or 600
VAC). Channel 1 is a hardware generated 100% FLA
(prevents pre-rotation vanes from further opening) or
104% FLA (closes pre-rotation vanes until motor cur-
rent is less than 102%) current limit override com-
mand that overrides normal Pro-rotation Vanes control.
Channels 2 through 4 are analog voltages that represent
phase A, B and C motor current. The highest phase is
Channels 5 through 7 are analog voltages that represent
phase A, B and C Line Voltage. The data for each chan-
nel is shown on the below.
4
5
GND
GND
Phase A
Phase A
motor
line
current
voltage
6
7
Peak
GND
Motor Current
(%FLA)
Phase B
Phase C
line
line voltage
voltage
53
4
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