Unit installation

Serial Communications

The TR16 Control Unit has a RS485 serial communications port. RS485 communications is two wire, half

duplex. Commands from remote systems can change the setpoint temperatures and mode of the

Thermostat. The Control Unit connects to the serial wiring via a 4 wire connector (with optional 12VDC

power). Serial commands received by the Control Unit can set a new setpoint or a new mode and are

sent to the WDU to update its display. When serial commands that update the setpoint or mode are

received, the WDU will switch it’s display to show the updated information for three seconds and then

return to the current temperature display.

TR16 Thermostats also responds to request for status by serial commands and can provide all thermostat

data and setup information as well as the current revisions of the WDU and Controller firmware.

Address Setting

The TR16 serial communications address is set from the Wall Display Unit by entering the setup mode.

To enter the setup mode, press and hold the Mode button and simultaneously press the Fan button. This

enters the setup mode and “Ad” will be displayed. Set the desired address by pressing the UP/DOWN

buttons until the desired address from 1 to 254 is selected. The default address is 1.

Serial Protocol

The TR16 thermostat has a robust serial protocol. It is based on a simple ASCII message format as

described in the RCS Serial Communications Protocol manual, DCN# 150-00225.

Note: NOT ALL of the commands/variables defined in the protocol document are applicable to the TR16,

check Section 8 of the protocol manual for details.

The following thermostat information can be sent to or requested from the thermostat by the serial

protocol.

• Temperature

• Heating setpoint

• Cooling setpoint

• System Mode

• Fan Mode

• F/C mode

• HVAC output status

• Network Address

• Any system variable

• System firmware revisions

Serial Communications Setup

To communicate to TR16 thermostats, set the communications parameters of the host system to: 9600

baud, no parity, 8 bits, 1 stop bit and No flow control.

Transmission delay. The TR16 will delay responses to request messages for 5mS to conform to the

RCS CommStar network protocol. This is necessary for RS485 half duplex devices to use Send Data

Control for automatic flow control.

DCN: 141-00930-09 7/13/06