neptronic CMU-Modbus Compact Make-up Air Unit
Introduction
The Compact Make-up Air Unit Modbus Communication Module User Guide provides information for using the Neptronic communication feature. The controller uses Modbus communication protocol over a serial line in the RTU mode and provides a Modbus network interface between client devices and Neptronic Compact Make-up Air Unit devices. The Compact Make-up Air Unit Modbus Guide assumes that you are familiar with Modbus terminology. The following are the requirements for Modbus:
- Data Model. The Compact Make-up Air Unit Modbus server data model uses only the Holding Registers table.
- Register Address:
- As per the protocol base (base 0); for PLC add 1 to the protocol base.
- As per the holding register (base 40001).
- Function Codes. The Compact Make-up Air Unit Modbus server supports a limited function codes subset comprising:
- Read Holding Registers (0x03)
- Write Single Register (0x06)
- Write Multiple Registers (0x10)
- Exception Responses. The Compact Make-up Air Unit Modbus server supports the following exception codes:
- Illegal data address
- Illegal data value
- Slave device busy
- Serial Line. The Compact Make-up Air Unit Modbus over serial line uses RTU transmission mode over a two-wire configuration RS485 (EIA/TIA-485 standard) physical layer.
- The physical layer can use fixed baud rate selection or automatic baud rate detection (default) as per the Modbus Auto Baud Rate device menu item or holding register index 1.
- The supported baud rates are 9600, 19200, 38400, 57600, and 76800 bps.
- The physical layer also supports variable parity control and stop-bit configuration as per the Modbus Comport Config device menu item or holding register index 2.
- In auto baud rate configuration, if the device detects only consecutive bad frames (2 or more) for one second with any given baud rate, it will reinitialize itself to the next baud rate.
- If the device does not detect any activity for one second or more, it will find a silent line to prevent a possible baud rate scan on the next frame it detects.
- Addressing. The Compact Make-up Air Unit device only answers at the following address:
- The device’s unique address (1 to 247) can be set through the device menu or by holding the register index
Holding Registers Table
Glossary
| Name | Description | Name | Description |
| W | Writable Register | ASCII | For registers containing ASCII (8-bit) characters |
| RO | Read Only Register | MSB | Most Significant Byte |
| Unsigned | For range of values from 0 to 65,535, unless otherwise specified | LSB | Least Significant Byte |
| Signed | For range of values from -32,768 to 32,767, unless otherwise specified | MSW | Most Significant Word |
| Bit String | For registers with multiple values using bit mask (example, flags) | LSW | Least Significant Word |
Holding Register Table
| Protocol Base | Holding Register |
Description |
Data Type |
Range |
Writable |
| 0 | 40001 | Modbus product type and address. | Unsigned | MB = Modbus Address (e.g. 110), LB = 1-247 | W |
| 1 | 40002 | Analog input 1 voltage. | Unsigned
Scale 1000 |
Unit: Volts (V), Range: 0V to 10V
Value x 1000 (e.g. 2V = 2000) |
RO |
| 2 | 40003 | Analog input 2 voltage. | Unsigned
Scale 1000 |
Unit: Volts (V), Range: 0V to 10V
Value x 1000 (e.g. 2V = 2000) |
RO |
| 3 | 40004 | Analog input 3 temperature. | Signed
Scale 100 |
Units: °C/°F, Range: -40°C to 85°C or -40°F to 185°F
Value x 100 (e.g. 25°C = 2500 or 25°F = 2500) |
RO |
| 4 | 40005 | Analog input 4 temperature. | Signed
Scale 100 |
Units: °C/°F, Range: -40°C to 85°C or -40°F to 185°F
Value x 100 (e.g. 25°C = 2500 or 25°F = 2500) |
RO |
| 5 | 40006 | Room air temperature value measured by TDF. | Unsigned
Scale 100 |
Units: °C/°F, Range : 0°C to 50°C or 32°F to 122°F
Value x 100 (e.g. 5°C = 500 or 50°F = 5000) |
RO |
| 6 | 40007 | Room air relative humidity value measured by TDF. | Unsigned
Scale 10 |
Unit: %RH, Range: 0 to 100%RH
Value x 10 (e.g. 10%RH = 100) |
RO |
| 7 | 40008 | Room CO2 concentration value measured by TDF. | Unsigned
Scale 1 |
Unit: PPM, Range: 0 to 2000 PPM
Value x 1 (e.g. 2 PPM = 2) |
RO |
| 8 | 40009 | The volatile organic compound index measured by TDF. | Unsigned
Scale 1 |
Unit: No Unit, Range: 0 to 65535,
Value x 1 (e.g. 100 = 100) |
RO |
| Protocol Base | Holding Register |
Description |
Data Type |
Range |
Writable |
| 9 | 40010 | Luminous flux measured by TDF. | Unsigned
Scale 1 |
Unit: Lux, Range: 0 to 16000 Lux
Value x 1 (e.g. 2 Lux = 2) |
RO |
| 10 | 40011 | CMU on-board potentiometer temperature setpoint. | Unsigned
Scale 100 |
Units: °C/°F, Range: 0°C to 35°C or 32°F to 95°F
Value x 100 (e.g. 2°C = 200 or 50°F = 5000) |
RO |
| 11 | 40012 | CMU intake temperature. | Signed
Scale 100 |
Units: °C/°F, Range: -40ºC to 85ºC or -40°F to 185°F
Value x 100 (e.g. 23°C = 2300 or 23°F = 2300) |
RO |
| 12 | 40013 | CMU outtake temperature. | Signed
Scale 100 |
Units: °C/°F, Range: -40ºC to 85ºC or -40°F to 185°F
Value x 100 (e.g. 23°C = 2300 or 23°F = 2300) |
RO |
| 13 | 40014 | CMU board temperature. | Signed
Scale 100 |
Units: °C/°F, Range: -40ºC to 85ºC or -40°F to 185°F
Value x 100 (e.g. 23°C = 2300 or 23°F = 2300) |
RO |
| 14 | 40015 | CMU SSR temperature. | Signed
Scale 100 |
Units: °C/°F, Range: -40ºC to 85ºC or -40°F to 185°F
Value x 100 (e.g. 23°C = 2300 or 23°F = 2300) |
RO |
| 15 | 40016 | AI3/BI3 multi-mode input state. | Unsigned | 0 = Open, 1 = Closed | RO |
| 16 | 40017 | AI4/BI4 multi-mode input state. | Unsigned | 0 = Open, 1 = Closed | RO |
| 17 | 40018 | Room movement detection occupancy sensor. | Unsigned | 0 = No, 1 = Yes | RO |
| 18 | 40019 | CMU On/Off contact input state. | Unsigned | 0 = Off, 1 = On | RO |
| 19 | 40020 | Analog output 1 voltage. | Unsigned
Scale 100 |
Unit: Volts, Range: 0V to 10V
Value x 100 (e.g. 3V = 300) |
RO |
| 20 | 40021 | Analog output 2 voltage. | Unsigned
Scale 100 |
Unit: Volts, Range: 0V to 10V
Value x 100 (e.g. 3V = 300) |
RO |
| 21 | 40022 | Binary output 1 state. | Unsigned | 0 = Open, 1 = Closed | RO |
| 22 | 40023 | Binary output 1 state. | Unsigned | 0 = Open, 1 = Closed | RO |
| 23 | 40024 | Supply air temperature. | Unsigned
Scale 100 |
Units: °C/°F, Range: 0°C to 100°C or 32°F to 212°F
Value x 100 (e.g. 2°C = 200 or 50°F = 5000) |
RO |
| 24 | 40025 | Supply air relative humidity. | Unsigned
Scale 100 |
Units: %RH, Range: 0 to 100%RH
Value x 100 (e.g. 23%RH = 2300) |
RO |
| 25 | 40026 | Outside air temperature. | Signed
Scale 100 |
Units: °C/°F, Range: -40ºC to 50ºC or -40°F to 122°F
Value x 100 (e.g. 23°C = 2300 or 23°F = 2300) |
RO |
| 26 | 40027 | Outside air relative humidity. | Unsigned
Scale 100 |
Units: %RH, Range: 0 to 100%RH
Value x 100 (e.g. 23%RH = 2300) |
RO |
| 27 | 40028 | Duct static pressure. | Unsigned
Scale 10 |
Units: Pascal (Pa), Range: 0 to 1250 Pa
Value x 10 (e.g. 50 Pa = 500) |
RO |
| Protocol Base | Holding Register |
Description |
Data Type |
Range |
Writable |
| 28 | 40029 | Damper position feedback. | Unsigned
Scale 1 |
Unit: %, Range: 0% to 100%,
Value x 1 (e.g. 100% = 100) |
RO |
| 29 | 40030 | Current airflow setpoint in percent of maximum capacity. | Unsigned
Scale 1 |
Unit: %, Range: 0% to 100%,
Value x 1 (e.g. 100% = 100) |
RO |
| 30 | 40031 | CMU ECM fan speed feedback value. | Unsigned
Scale 1 |
Unit: RPM, Range: 0 to 10000 RPM,
Value x 1 (e.g. 100 RPM = 100) |
RO |
| 31 | 40032 | Heater vernier stage duty cycle. | Unsigned
Scale 10 |
Unit: %, Range: 0 to 100%,
Value x 10 (e.g. 100% = 1000) |
RO |
| 32 | 40033 | Network temperature setpoint. | Unsigned
Scale 100 |
Unit: °C/°F, Range: 0°C to 35°C or 32°F to 95°F,
Value x 1 (e.g. 5°C = 500 or 50°F = 5000) |
W |
| 33 | 40034 | TDF temperature setpoint. | Unsigned
Scale 100 |
Unit: °C/°F, Range: 0°C to 35°C or 32°F to 95°F,
Value x 1 (e.g. 5°C = 500 or 50°F = 5000) |
W |
| 34 | 40035 | CMU anti-freeze setpoint. | Unsigned
Scale 100 |
Unit: °C/°F, Range: 0°C to 35°C or 32°F to 95°F,
Value x 1 (e.g. 5°C = 500 or 50°F = 5000) |
W |
| 35 | 40036 | Occupied airflow setpoint in percent of maximum capacity. | Unsigned
Scale 1 |
Unit: %, Range: 0 to 100%,
Value x 1 (e.g. 100% = 100) |
W |
| 36 | 40037 | Unoccupied airflow setpoint in percent of maximum capacity. | Unsigned
Scale 1 |
Unit: %, Range: 0 to 100%,
Value x 1 (e.g. 100% = 100) |
W |
| 37 | 40038 | Binary input 3 stage weight. | Unsigned
Scale 1 |
Unit: %, Range: 0 to 100%,
Value x 1 (e.g. 100% = 100) |
W |
| 38 | 40039 | Binary input 4 stage weight. | Unsigned
Scale 1 |
Unit: %, Range: 0 to 100%,
Value x 1 (e.g. 100% = 100) |
W |
| 39 | 40040 | Exhaust fan start delay. | Unsigned
Scale 1 |
Unit: Seconds, Range: 1 to 255 seconds
Value x 1 (e.g. 10 secs = 10) |
W |
| 40 | 40041 | Exhaust fan control signal minimum value. | Unsigned
Scale 100 |
Unit: Volts (V), Range: 0 to 10V,
Value x 100 (e.g. 3V = 300) |
W |
| 41 | 40042 | Exhaust fan control signal maximum value. | Unsigned
Scale 100 |
Unit: Volts (V), Range: 0 to 10V,
Value x 100 (e.g. 3V = 300) |
W |
| 42 | 40043 | Damper stroke time. | Unsigned
Scale 1 |
Unit: Seconds, Range: 1 to 255 seconds,
Value x 1 (e.g. 100 secs = 100) |
W |
| 43 | 40044 | Occupancy inputs minimum time. | Unsigned
Scale 1 |
Unit: Minutes, Range: 0 to 240 minutes,
Value x 1 (e.g. 10 mins = 10) |
W |
| Protocol Base | Holding Register |
Description |
Data Type |
Range |
Writable |
| 44 | 40045 | Temperature setpoint minimum value. | Unsigned
Scale 100 |
Unit: °C/°F, Range: 0°C to 35°C or 32°F to 95°F,
Value x 1 (e.g. 5°C = 500 or 50°F = 5000) |
W |
| 45 | 40046 | Temperature setpoint maximum value. | Unsigned
Scale 100 |
Unit: °C/°F, Range: 0°C to 35°C or 32°F to 95°F,
Value x 1 (e.g. 5°C = 500 or 50°F = 5000) |
W |
| 46 | 40047 | Dry mode relative humidity setpoint. | Unsigned
Scale 1 |
Unit: %RH, Range: 10 to 90%RH
Value x 1 (e.g. 10%RH = 10) |
W |
| 47 | 40048 | Dry mode relative humidity setpoint dead band. | Unsigned
Scale 1 |
Unit: %RH, Range: 1 to 10%RH
Value x 1 (e.g. 10%RH = 10) |
W |
| 48 | 40049 | Occupied static pressure control loop setpoint. | Unsigned
Scale 10 |
Unit: Pascal (Pa), Range: 0 to 1250 Pa
Value x 10 (e.g. 3 Pa = 30) |
W |
| 49 | 40050 | Unoccupied static pressure control loop setpoint. | Unsigned
Scale 10 |
Unit: Pascal (Pa), Range: 0 to 1250 Pa
Value x 10 (e.g. 3 Pa = 30) |
W |
| 50 | 40051 | CO2 concentration setpoint. | Unsigned
Scale 1 |
Unit : PPM, Range : 0 to 1000 PPM
Value x 1 (e.g. 3 PPM = 3) |
W |
| 51 | 40052 | CO2 concentration setpoint dead band. | Unsigned
Scale 1 |
Unit : PPM, Range : 0 to 200 PPM
Value x 1 (e.g. 3 PPM = 3) |
W |
| 52 | 40053 | Supply air temperature offset. | Signed
Scale 100 |
Unit: °C/°F, Range: ± 5ºC or +/-9ºF
Value x 100 (e.g. 2ºC = 200 or 3ºF = 300) |
W |
| 53 | 40054 | Supply air temperature humidity offset. | Signed
Scale 100 |
Unit: %RH, Range: ± 5%RH Value x 100 (e.g. 2%RH = 200) | W |
| 54 | 40055 | Outside air temperature offset. | Signed
Scale 100 |
Unit: °C/°F, Range: ± 5ºC or +/-9ºF
Value x 100 (e.g. 2ºC = 200 or 3ºF = 300) |
W |
| 55 | 40056 | Outside air temperature humidity offset. | Signed
Scale 100 |
Unit: %RH, Range: ± 5%RH Value x 100 (e.g. 2%RH = 200) | W |
| 56 | 40057 | Room air temperature offset. | Signed
Scale 100 |
Unit: °C/°F, Range: ± 10ºC or ± 18ºF Value x 100 (e.g. 2ºC = 200 or 3ºF = 300) | W |
| 57 | 40058 | Room air relative humidity offset. | Signed
Scale 100 |
Unit: %RH, Range: ± 5%RH Value x 100 (e.g. 2%RH = 200) | W |
| 58 | 40059 | Static pressure offset. | Signed
Scale 10 |
Unit: Pascal (Pa), Range: ± 125 Pa Value x 10 (e.g. 2 Pa = 200) | W |
| 59 | 40060 | Minimum fan speed. | Unsigned
Scale 1 |
Unit: %, Range: 0 to 100%
Value x 1 (e.g. 3% = 3) |
W |
| Protocol Base | Holding Register |
Description |
Data Type |
Range |
Writable |
| 60 | 40061 | Temperature control proportional band. | Unsigned
Scale 100 |
Unit: °C/°F, Range: 0.5°C to 20°C or 33°F to 68°F,
Value x 100 (e.g. 5°C = 500 or 50°F = 5000) |
W |
| 61 | 40062 | Temperature control integral time. | Unsigned
Scale 1 |
Unit: Seconds, Range: 0 to 255 seconds,
Value x 1 (e.g. 100 secs = 100) |
W |
| 62 | 40063 | Temperature control derivate time. | Unsigned
Scale 1 |
Unit: Seconds, Range: 0 to 255 seconds,
Value x 1 (e.g. 100 secs = 100) |
W |
| 63 | 40064 | Static pressure control proportional band. | Unsigned
Scale 1 |
Unit: Pascal (Pa), Range: 0 to 250 Pa
Value x 1 (e.g. 3 Pa = 3) |
W |
| 64 | 40065 | Static pressure control integral time. | Unsigned
Scale 1 |
Unit: Seconds, Range: 0 to 255 seconds,
Value x 1 (e.g. 100 secs = 100) |
W |
| 65 | 40066 | Static pressure control derivate time. | Unsigned
Scale 1 |
Unit: Seconds, Range: 0 to 255 seconds,
Value x 1 (e.g. 100 secs = 100) |
W |
| 66 | 40067 | Control band. | Unsigned
Scale 100 |
Unit: °C/°F, Range: 2°C to 10°C or 36°F to 50°F,
Value x 100 (e.g. 5°C = 500 or 50°F = 5000) |
W |
| 67 | 40068 | Modbus timeout. | Unsigned
Scale 1 |
Unit: Seconds, Range: 15 to 1800 seconds,
Value x 1 (e.g. 100 secs = 100) |
W |
| 68 | 40069 | Number of synchronization timeouts. | Unsigned
Scale 1 |
Unit: No Unit, Range: 0 to 65535,
Value x 1 (e.g. 100 = 100) |
W |
| 69 | 40070 | No heat detection deadband. | Unsigned
Scale 100 |
Unit: °C/°F, Range: 2°C to 8°C or 36°F to 46°F,
Value x 100 (e.g. 5°C = 500 or 5°F = 500) |
W |
| 70 | 40071 | No heat detection delay. | Unsigned
Scale 1 |
Unit: Seconds, Range: 30 to 240 seconds,
Value x 1 (e.g. 100 secs = 100) |
W |
| 71 | 40072 | Exhaust fan state. | Unsigned | 0 = Off, 1 = On | RO |
| 72 | 40073 | On/Off damper state. | Unsigned | 0 = Closed, 1 = Open | RO |
| 73 | 40074 | On/Off damper feedback. | Unsigned | 0 = Closed, 1 = Open | RO |
| 74 | 40075 | CMU fan enable. | Unsigned | 0 = No, 1 = Yes | RO |
| 75 | 40076 | CMU heater stage 2 state. | Unsigned | 0 = Off, 1 = On | RO |
| 76 | 40077 | Binary input 3 contact type. | Unsigned | 0 = NO, 1 = NC | W |
| 77 | 40078 | Binary input 4 contact type. | Unsigned | 0 = NO, 1 = NC | W |
| 78 | 40079 | Binary output 1 contact type. | Unsigned | 0 = NO, 1 = NC | W |
| 79 | 40080 | Binary output 2 contact type. | Unsigned | 0 = NO, 1 = NC | W |
| Protocol Base | Holding Register |
Description |
Data Type |
Range |
Writable |
| 80 | 40081 | Enable occupancy inputs. | Unsigned | 0 = No, 1 = Yes | W |
| 81 | 40082 | Dry mode. | Unsigned | 0 = Disable, 1 = Enable | W |
| 82 | 40083 | CO2 extract. | Unsigned | 0 = Disable, 1 = Enable | W |
| 83 | 40084 | Static pressure loop. | Unsigned | 0 = Disable, 1 = Enable | W |
| 84 | 40085 | Occupancy inactive mode. | Unsigned | 0 = Unoccupied, 1 = Off | W |
| 85 | 40086 | CMU occupancy state. | Unsigned | 1 = Occupied | 2 = Unoccupied | 3 = Off | W |
| 86 | 40087 | Temperature setpoint source. | Unsigned | 1 = On Board | 2 = TSTAT | 3 = Network | W |
| 87 | 40088 | AI1 input mode. | Unsigned | 1 = Off | 2 = SAT | 3 = SARH | 4 = OAT | 5 = OARH | 6 = Static Pressure | 7 = Fan Setpoint | 8 = Damper Feedback | W |
| 88 | 40089 | AI2 input mode. | Unsigned | 1 = Off | 2 = SAT | 3 = SARH | 4 = OAT | 5 = OARH | 6 = Static Pressure | 7 = Fan Setpoint | 8 = Damper Feedback | W |
| 89 | 40090 | AI3/BI3 input mode. | Unsigned | 1 = Off | 2 = SAT | 3 = OAT | 4 = Damper Feedback | 5 = Occupancy | 6 = Fan Speed Stage | W |
| 90 | 40091 | AI4/BI4 input mode. | Unsigned | 1 = Off | 2 = SAT | 3 = OAT | 4 = Damper Feedback | 5 = Occupancy | 6 = Fan Speed Stage | W |
| 91 | 40092 | AO1 output mode. | Unsigned | 1 = Off | 2 = Exhaust Fan | 3 = Damper | W |
| 92 | 40093 | AO2 output mode. | Unsigned | 1 = Off | 2 = Exhaust Fan | 3 = Damper | W |
| 93 | 40094 | BO1 output mode. | Unsigned | 1 = Off | 2 = Exhaust Fan | 3 = Damper | W |
| 94 | 40095 | BO2 output mode. | Unsigned | 1 = Off | 2 = Exhaust Fan | 3 = Damper | W |
| 95 | 40096 | Static pressure sensor range. | Unsigned | 1 = 250 Pa | 2 = 500 Pa | 3 = 1250 Pa | W |
| 96 | 40097 | Analog input 1 signal range. | Unsigned | 1 = 2-10Vdc | 2 = 0-10Vdc | W |
| 97 | 40098 | Analog input 2 signal range. | Unsigned | 1 = 2-10Vdc | 2 = 0-10Vdc | W |
| 98 | 40099 | Analog output 1 signal range. | Unsigned | 1 = 2-10Vdc | 2 = 0-10Vdc | W |
| 99 | 40100 | Analog output 2 signal range. | Unsigned | 1 = 2-10Vdc | 2 = 0-10Vdc | W |
| 100 | 40101 | Control temperature source. | Unsigned | 1 = SAT | 2 = RAT | W |
| 101 | 40102 | LCD screen top line value. | Unsigned | 1 = None | 2 = Time | 3 = CO2 | 4 = SARH | 5 = RARH | W |
| 102 | 40103 | LCD screen displayed temperature. | Unsigned | 1 = Default | 2 = Alternate | 3 = SAT | 4 = TSTAT | W |
| 103 | 40104 | LCD screen last reset reason. | Unsigned | 1 = No reason | 2 = Independent Watchdog | 3 = Window Watchdog | 4 = Software Reset | 5 = Power Down | RO |
| Protocol Base | Holding Register |
Description |
Data Type |
Range |
Writable |
|
|
104 |
40105 |
Alarm status. |
Bit String |
B0 = Unblocking Damper Required B1 = SSOR1 Sens Not Detected B2 = SSOR2 Sens Not Required B3 = SAT Not Detected
B4 = RAT Not Detected |
B5 = Timeout Comm B6 = AI1 Reading Error B7 = AI2 Reading Error
B8 to B31 = Reserved |
RO |
|
105 |
40106 |
System alarm host. |
Bit String |
B0 = Thermal Cutout B1 = Comm Timeout
B3 = Heater Temp Cutout B4 = SSR Temp Cutout B5 = Board Temp Cutout B6 = Duct Temp Cutout B7 = Heater Temp 1 Failure B8 = Heater Temp 2 Failure B9 = Board Temp Failure B10 = SSR Temp Failure |
B11 = TRL Failure B13 = Invalid Config
B14 = Fan Temp Failure B16 = External Temp Failure B17 = Supply Temp Failure B22 = Fan Feedback Error B30 = Air Flow Not Detected B31 = Heat Not Detected B2, B12, B15, B18 to B21, B23 to B29 = Reserved |
RO |
400 Lebeau blvd, Montreal, Qc, H4N 1R6, Canada www.neptronic.com
Toll-free in North America: 1-800-361-2308
Tel.: 514-333-1433
Fax: 514-333-3163
Customer service fax: 514-333-1091
Monday to Friday: 8:00 am to 5:00 pm (Eastern time)
Documents / Resources
 |
neptronic CMU-Modbus Compact Make-up Air Unit [pdf] User Guide CMU-Modbus, Compact Make-up Air Unit, Make-up Air Unit, Compact Air Unit, Air Unit, CMU-Modbus |
