VICI Selectors (multiposition) Microelectric - Manual (Page 8)

8
Serial Communication Protocol
Serial communication is based on an ASCII string protocol. Carriage
return (OD hex) characters parse the communications by defining the
end of each command. Line feed characters (OA hex) are ignored.
A three-pin connector is used for the RS-232 interface: pin assign-
ments are indicated at right. Software flow control (Xon/Xoff) and hard-
ware handshaking are not supported.
With the software-settable device “ID” feature enabled, the serial port output (transmit line) of the
actuator is disabled (high impedance). Thus, as many as ten actuators can be controlled from a single
host serial port for a temporary multidrop application. For permanent multidrop applications, the
RS-485 option is the factory-recomended solution. The table on the previous page describes and
explains all the commands available.
Using the Device ID Feature
Actuators are shipped from the factory with this feature disabled. When it’s enabled, the actuator
responds only to commands which begin with the correct ID prefix, allowing up to 10 actuators to be
controlled from one serial port. A single command can be broadcast to all actuators by using an
asterisk (*) as the command prefix.
Note: Any broadcast command which elicits a response from the
serial port (such as *VR or *ID1) will receive a combined and unintelligible response.
To set the ID of an actuator, connect it to an RS-232 serial port as shown in Figure 1 on page 2.
Caution: When installing or replacing actuators on a shared serial port, make sure that no two
devices have been set to the same ID number.
1. Remove all of the actuators from the serial daisy chain except the one for which you are setting the ID.
2. Type VR <enter>. You should get a response giving the firmware version, indicating that serial
communication with the actuator is established. If there is no response, type *VR<enter> to see
if the ID is already set. If there is still no response, check the cabling and connections.
3. To set an ID, type IDn<enter>, where n is the new ID, from 0 to 9.
To change an ID, type i ID n<enter>, where i is the current ID and n is the new ID.
To disable the ID feature, type i ID*<enter>, where i is the current ID.
Setting a New Baud Rate
To permanently set a new baud rate for the actuator:
1. Establish communications with the actuator at the current baud rate.
2. Issue the command SB nnnn to temporarily change the baud rate to the desired rate. If the power
goes down at this point, the baud rate will revert to the last permanent setting.
3. Change the host computer to the same baud rate just set in the actuator, and verify that you can
establish communications.
4. Re-issue the same SB nnnn command you did previously (in Step 2), and the current baud will be
made permanent.
Using the Offset Feature
This feature makes it possible to control more than one actuator without increasing the number of
BCD input lines. The actuator’s SO value can be set from “1” to “96”, minus the current NP value (the
number of positions the actuator is set to index). Once an SO value is set, that value is the first (or
lowest) position an actuator will recognize. The factory SO setting is “1”, so an actuator with an NP
value of 10 responds to move commands for positions “1” to “10”. If the SO value is changed to “10”,
Serial Port (RS-232) Cable
Pin # Signal Description
1 Ground
2 Transmit to host
3 Receive from host