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DMC-3425 Chapter 4 Communication• 47
situations; using Local Mode for setup and testing is useful since this isolates the controller. Specific
modes of motion require operation in Local Mode. Also, each controller can have a program,
including the slave controllers. When a slave controller has a program, this program would always
operate in Local Mode.
Operation of Distributed Control
For most commands it is not necessary to be conscious of whether an axis is local or remote. For
instance to set the KP value for the A and C axes, the command to the master would be
KP 10,,20
Similarly, the interrogation commands can also be issued. For example, the position error for all axes
would be TE. The position operand for the F axis would be_TPF.
Some commands inherently are sent to all controllers. These include commands such as AB (abort),
CN and TM. In addition, the * may be used to send commands to all controllers. For example
SP*=1000
will send a speed of 1000 cts/sec to all axes. This syntax may be used with any configuration or
parameter commands.
Certain commands need to be launched specifically. For this purpose there is the SA command. In its
simplest form the SA command is
SAh= "command string"
Here "command string" will be sent to handle h. For example, the SA command is the means for
sending an XQ command to a slave/server. A more flexible form of the command is
SAh= field1,field2,field3,field4 ... field8
where each field can be a string in quotes or a variable.
For example, to send the command KI,,5,10; Assume var1=5 and var2=10 and send the command:
SAF= "KI",var1,var2
When the Master/client sends an SA command to a Slave/server, it is possible for the master to
determine the status of the command. The response _IHh4 will return the number 1 to 4. One means
waiting for the acknowledgement from the slave. Two means a colon (command accepted) has been
received. Three means a question mark (command rejected) has been received. Four means the
command timed out.
If a command generates responses (such as the TE command), the values will be stored in _SAh0 thru
_SAh7. If a field is unused its _SA value will be -2^31.
Accessing the I/O of the Slaves
The I/O of the server/slaves is settable and readable from the master. The bit numbers are adjusted by
the handle number of the slave controller. Each handle adds 100 to the bit number. Handle A is 100
and handle H is 800. In a TCP/IP control setup with two handles per slave, Galil recommends using
the value of the first handle for simplicity. In a UDP system, the single handle per slave is used to
address the I/O.
The command TZ can be used to display all of the digital I/O contained in a distributed control system.
Any IOC-7007’s configured using the HC command will also be displayed with the TZ command. See
the Command Reference for more information on the TZ command.