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Network/Modbus Communications
77
Variable Name
Variable
Address
Input Provided to Master System
Integer DDC system
receives
Pressure Set point
24
Pressure control set point
Displayed in ft/min.
Min Vent Set point
25
Minimum flow set point for ventilation.
Displayed in CFM.
Cooling Flow
26
Minimum flow set point for temperature
control.
Displayed in CFM.
Unoccupied Min Set
point
27
Unoccupied (Setback) minimum flow
set point.
Displayed in CFM.
Low Alarm
28
Low pressure alarm set point
Displayed in ft/min.
High Alarm
29
High pressure alarm set point
Displayed in ft/min.
Min Supply Alarm
30
Minimum supply flow alarm
Displayed in CFM.
Max Exhaust Alarm
31
Maximum general exhaust alarm
Displayed in CFM.
Min Offset Set point
32
Minimum offset set point
Displayed in CFM.
Max Offset Set point
33
Maximum offset set point
Displayed in CFM.
Max Supply Set point 34
Maximum supply set point
Displayed in CFM.
Min Exhaust Set
point
35
Minimum exhaust set point
Displayed in CFM.
Temp Set point
36
Temperature set point
Displayed in
°
F
Unoccupied Temp
Set point
55
Unoccupied (Setback) temperature set
point
Displayed in
°
F
Supply Damper
Position
64
Current damper position for supply
control
0 to 100%
Exhaust Damper
Position
65
Current damper position for exhaust
control
0 to 100%
Reheat Valve
Position
66
Current valve position for temperature
control
0 to 100%
Units
106
Current pressure units displayed
0 Feet per minute
1 meters per second
2 inches of H
2
O
3 Pascal
*Note: Items in
italics
are
read only
variables.
EXAMPLE of
16 (10 Hex) Preset Multiple Regs
function format:
This example changes the minimum ventilation set point to 1000 CFM
QUERY
RESPONSE
Field
Name
(Hex)
Field
Name
(Hex)
Slave
Address
01
Slave
Address
01
Function 10
Function 10
Starting Address Hi
00
Starting Address Hi
00
Starting Address Lo
19
Starting Address Lo
19
No. Of Registers Hi
00
No. of Registers Hi
00
No. Of Registers Lo
01
No. of Registers Lo
01
Data Value (High)
03
Error Check (CRC)
--
Data Value (Low)
E8
Error Check (CRC)
--
Example of
03 Read Holding Registers
function format:
This example reads the total supply and total exhaust.