Master-To-Master (M2M)
95
NetLinx Programming Language Reference Guide
Control/NetLinx Language Support
The features of control to M2M include channel control (PUSH/RELEASE/ON/OFF/TO), level control,
send commands, and send strings.
Channel controls allow one NetLinx master to
PUSH/RELEASE a channel on a device of another system
via the
DO_PUSH/DO_RELEASE functions. Additionally, ON, OFF, TO, and feedback statements can
control channels on devices of remote systems. If a channel has a characteristic modifier associated with
it, that modifier still applies to the channel, regardless of whether the channel is manipulated locally or
remotely. For example, if a group of channels and variables is mutually exclusive, an
ON to one of the
channels will turn off all other channels and variables in the group prior to turning on the desired
channel.
Levels, strings, and commands are forwarded to the destination device.
Note that control is not limited to physical devices, and NetLinx program defined virtual devices may
also be manipulated by a remote system. This allows a local system to define a virtual device that can
receive
PUSH/RELEASEs, ONs, OFFs, etc. and make program decisions based upon that control.
Additionally, notification of control messages is not limited to "mainline" functions like
PUSH and
RELEASE; rather, all EVENT based code will operate normally regardless of the source of the original
control message/function.
Design considerations and constraints
In order to reference devices of other NetLinx systems, the devices must be defined in the
DEFINE_DEVICE section of the NetLinx program. Conversely, only devices that are necessary should
be placed in the
DEFINE_DEVICE section to avoid any unnecessary network traffic between NetLinx
masters.
 DEFINE_LATCHING - A remote device's channel is not allowed in the DEFINE_LATCHING
section.
 DEFINE_MUTUALLY_EXCLUSIVE- A remote device's channel is not allowed in the
DEFINE_MUTUALLY_EXCLUSIVE section.
 DEFINE_TOGGLING - A remote device's channel is not allowed in the DEFINE_TOGGLING
section.
The proper way to modify a channel's behavior is to place the modifiers in the remote device's master.
General Master-to-Master Issues
When multiple masters exist within a large NetLinx installation, the significance of the System number
component cannot be over emphasized. Out of habit, it is easy to ignore the system field within NetLinx
Studio because its value has not meant anything in the past.
When NetLinx Studio connects to a single master, yet allows the user to access all other system masters,
some confusion will occur. Therefore, it is a good idea to document each system's, number and the
topology of the interconnections.
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