Dwyer 16A User Manual
Page 17
Page 17
est
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Pid
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OPERATION AND PROGRAMMING OF OPTIONS
Option 992, 993, 995, 996 Serial Communication
The serial communications options allow the control to be written to and read from
a remote computer or other similar digital device. Communication is allowed either
through a RS-485 (Option 992, 996) port, or a RS-232 (Option 993, 995) port.
Wire the communication lines as shown on Page 7. Wiring for the RS-485 is run from
control to control in a daisy chain fashion with a termination resistor (120 ohms)
across the transmit and receive terminals 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.
NOTE: THE BAUD RATE AND ADDRESS MENU ITEM SETTINGS WILL TAKE
EFFECT ON THE NEXT POWER UP OF THE CONTROL. BE SURE TO TURN THE
POWER TO THE CONTROL OFF AND ON BEFORE USING THE NEW BAUD RATE
AND ADDRESS VALUES.
In operation, you have the option of preventing a write command from the host com-
puter. To prevent the host from writing to the control change the
L0rE
menu item in
the Secondary Menu to
L0C
. To allow the host to write commands to the control set
L0rE
to
rE
. (The host does have the ability to change the
L0rE
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
L0rE
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 message
CHEC L0rE
.
To clear the message set
L0rE
to
L0C
.
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