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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 de-tailed
explanation of each board. Both boards contain an 8
channel multiplexer. The microprocessor sequen-tially
and continually reads channels 0 through 7. It reads
each channel by applying a 3-bit binary address to the
multiplexer.
TABLE 9 - 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 5 - MICROBOARD 031-03630-001
A 0 to 5 VDC analog value is returned from each chan-
nel. The function of each is in Table 9 on page 79.
The microprocessor determines which board, and
therefore which starter is present, by the value returned
from channel 0. Since channels 0 through 6 are ground-
ed, 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 mo-tor
current 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
79
5
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