Dwyer 32A - Manual (Page 15)

Page 15
OPERATION AND PROGRAMMING OF OPTIONS
Option 992, Serial Communication.
The serial communications option allows the control to be written to and read from a remote comput-
er or other similar digital device. Communication is allowed through a RS-485 (Option 992) port.
Wire the communication lines as shown on Page 6. Wiring for the RS-485 is run from control to con-
trol in a daisy chain fashion with a termination resistor (120 ohms) across the transmit and receive ter-
minals of the last control in the chain.
Select the control address and communication baud rate with the Addr and bAUd menu items in the
Secure Menu. THE BAUD RATE AND ADDRESS MENU ITEMS WILL TAKE EFFECT ON THE NEXT
POWER UP OF THE CONTROL. BE SURE TO POWER CYCLE THE CONTROL BEFORE USING
THE NEW BAUD RATE AND ADDRESS.
In operation, you have the option of preventing a write command from the host computer. To prevent
the host from writing to the control change the LOrE menu item in the Secondary Menu to LOC. To
allow the host to write commands to the control set LOrE to rE. (The host does have the ability to
change the LOrE state, but it is not automatic.)
If your system depends on constant reading or writing to and from the host, you may wish to set the
No Activity Timer (nAt) to monitor the addressing of the control. When the LOrE is set to rE and the
nAt is set to any value other than Off, the control will expect to be addressed on a regular basis. If the
control is not addressed in the time set by the value of nAt, then the control will display the error mes-
sage CHEC LOrE. To clear the message set LOrE to LOC.
CHANGING PROGRAMMING
FOR SET POINT 2 AND ALARM
Either Set Point 2 or the Alarm function as the second output of the 32A. The ordering code determines
whether the second output operates as a second set point or alarm.
When the 32A second output is programmed as Control, SP2 appears in the Primary Menu and the
appropriate SP2 related menu items appear in the Secondary and Secure Menus. When the 32A sec-
ond output is programmed as ALarm, the alarm related menu items appear in the Secondary and
Secure Menus.
If you have a control with a second output and wish to change the function of the second output from
ALarm to Control (or vice versa) use the Factory Default procedure.