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Serial communication
Serial communication includes:
• RS485 com port
• RS485 address
• RS485 protocol
• Thermostat network commands
RS485 com port
The thermostat has a RS485 serial com port. This is a two-wire (plus ground), half-duplex communication
network. Typically, the thermostat will be used on the SmartCommand network and connected to the Smart
Command automation controller.
The RS485 com port communication setup is 9600 baud, 8 data bits, 1 stop bit, and no parity. Flow control is
set to None.
Transmission delay
The thermostat will delay responses to request messages for 5 msec to conform to the SmartCommand network
protocol. This is necessary for RS485 half-duplex devices to use send data control for automatic flow control.
RS485 address
You can check the network address setting of the thermostat by pressing Menu to open the main Menu screen.
Scroll down to the Thermostat info menu item and press Select. The Thermostat information screen on page 16
will show the current network address of the thermostat. The default network address is 1.
Changing the network address
The network address is set from the Installer settings screen on page 17 on the WDU. This is a hidden menu
and does not appear in the main Menu screen selections. To change the network address, do the following:
1. Press Menu to open the Main menu screen on page 7.
2. While in the Menu screen, press and hold the middle two control buttons on the WDU for five seconds
until the Installer settings screen on page 17 opens.
3. Scroll down to the Network menu item in the Installer settings screen and press Select. You can set the
network address from 1 to 254.
Note: Network address 0 is reserved for the host system address and 255 is reserved for global commands.