15
7.2 HVAC Status and Control Registers
The Black Pear TM-64x behaves as 24 modbus slaves. Slaves 1 to 22 each have 90
registers (Offset = 0 to 89). Slaves 23 and 24 are used for configuration.
The default ‘Base Slave Address’ is 1, meaning the Black Pear will respond to msgs for
slaves 1 to 24. The Base Slave Address can be adjusted from 1 up to 200. A setting of 200
means the Black Pear will respond to msgs for slaves 200 to 223.
This is useful to prevent address clashing when the Black Pear unit is attached to a serial
communications network containing multiple Modbus devices.
Some BMS systems have limited slave address resources, so the ‘Single Slave Access’
feature means the Black Pear can be configured to respond to just 1 slave address
(i.e. the ‘Base Slave Address’ setting).
The Black Pear maps the data from the air conditioner units into Modbus registers
accessed by two Modbus parameters ‘Slave No.’ and ‘Offset’.
All slave numbers referred to in this document assume the default Base Address.
Slaves 1 to 21 each represent 3 units, and slave 22 represents 1 unit.
Each slave is organised as follows:
General Information
Extended Information
Extra Information
Unit A
Unit B
Unit C
Unit A
Unit B
Unit C
Unit A
Unit B
Unit C
Offset 0 Offset 10 Offset 20
Offset 30 Offset 40 Offset 50
Offset 60 Offset 70 Offset 80
General information for a
single unit
Extended information for a
single unit
Extra information for a
single unit
Register
Offset
Stored Value
Register
Offset
Stored Value
Register
Offset
Stored Value
0
Return Air Temp
0
Air Direction (R)
0
‘Hi-res’ Return Air
1
Error Code
1
Air Direction (W)
1
‘Hi-res’ Setpoint (R)
2
Setpoint (R)
2
Inhibit (R)
2
‘Hi-res’ Setpoint (W)
3
Mode (R)
3
Inhibit (W)
3
Unused
4
Fan Speed (R)
4
Ventilation (R)
4
Unused
5
Setpoint (W)
5
Ventilation (W)
5
Unused
6
Mode (W)
6
Error Code (DispA)
6
Unused
7
Fan Speed (W)
7
Error Code (DispB)
7
Unused
8
On/Off (R)
8
Reserved
8
Unused
9
On/Off (W)
9
Unused
9
Unused
See Section 7.5 for an overview of Modbus slave and offset usage..
Examples:
1) To read the current fan speed of unit 8
Single Slave Access = Off
Single Slave Access = On
Slave Function Offset
Slave Function Offset
3
3
14 1
3
194
2) To read the current mode of unit 48
Single Slave Access = Off
Single Slave Access = On
Slave Function Offset
Slave Function Offset
16 3 23
1 3
1373
Not currently supported
