Computer Interfacing 49
monitoring the scan status via “SD?” command. Once the scan is completed, the
master controller can be queried to find out the addresses of all the slave controllers.
NOTE: The Picomotor Windows software application (version 2.0 and above)
provides the quickest and easiest path to controller address configuration. The
user friendly software will automatically report any RS-485 address conflicts
found and offer easy resolution options.
The Remote Command Set chapter provides a detailed description of the commands
used to setup the RS-485 network.
The 8742 provides various commands to help setup the RS-485 network. (See
below)
COMMAND DESCRIPTION
SA Set controller address
SA? Controller address query
SC Initiate scan process
SC? Scan result query
SD? Scan status query
Table 3 RS-485 LAN Related Commands
5.5.2 Communication with a Slave Controller
All the commands intended for a slave controller connected via RS-485 LAN must have a
slave controller address prefix added to the command. For example, to query the motion
status of motor 2 on a slave controller with address 3, the host PC must send “3>2MD?”
command to the master controller via Ethernet or USB. In this command, “3>” is the
slave controller address prefix. This prefix tells the master controller that the command
“2MD?” is intended for slave controller with address 3 on the RS-485 LAN.
When the master controller sends a response back to host PC, it too will have a slave
controller address prefix. This is used to inform the host that the response came from a
slave controller with that address. For example, the response received by a host PC to the
above mentioned command might be “3>1”. This indicates that the motion of motor #2
in slave controller with address 3 is complete.
NOTE: RS-485 LAN transmission speed is 115 Kbit/s (~100 µs/character)
If a command does not have controller address prefix, the master controller will assume
that the command is addressed it and process the same.
NOTE: The host PC is effectively the ‘master’ in the special case of direct LAN
connection via RS485-to-RS232 adapter/converter configuration
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