Channels (Bozza)

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JSup I/O system is organizes in channels that group tag I/O hooks and defines the way they are read/written.

Every channel is bound to a driver and to a driver specific a device.

Some features:

Channels can perform timed or triggered read or event unsolicited read (according to the protocol/driver capabilities).
Channel read can be requested by a window.
Writes can be triggered and/or done on tag change.

Channels are comparable with FactoryLink I/O tables.

The Channel list can be accessed with the menu Tools / Edit channels (or Ctrl+H keys).

Channel configuration

/img/JSup/iochannel_edit.png

The I/O driver that the channel has to use for its communication, it cannot be changed once the channel is created.
Name: an unique name that will identify the channel.
Drive dependent info: a button that open a driver specific dialog that provide configuration about the device and driver specific configuration of the channel.
Item prefix: a fixed text that will be prepended to every item of the channel I/O hooks, this can be useful for some drivers (SNMP or MQTT) to not to have to include a fixed prefix to every I/O hook.
Channel active condition: can be a constant or calculated expression that enable / disable the channel at all if, for example, a channel have to be active only on a certain JSup server or if you want to disable a channel at all but you don't want to delete it.
Block read: a block read requesta all I/O hooks value (except for write only I/O hooks) from the remote device, when the Block read trigger expression changes to a non false (or 0) value.
The Block read trigger is normally a single tag forced to true (or 1) to perform the read.
The End read tag, if specified, is a tag that will be forced to true if all the I/O hooks have been read successfully, or forced to false if the block read is not successful (even if I/O hooks are partially read: some read and some not). This tag will receive also the status of a Continuous read completion.
Continuous read: a timed basis read that can be enabled with a constant or variable expression (Read enable condition) and repeated at a given millisecond rate (Update time: constant or an expression). Some driver enable the possibility to read only active items, the I/O hooks of listened tags (the ones those are displayed in active window). Active windows can specify the read of one (or more) channels and the requested rate: the shorted rate will be used.
Block write: all the I/O hooks of the channel (except the read only ones) can be written at once when the Block write trigger expression (normally a single boolean tag) changes to a true (or non zero) value.
The End write tag, if specified, will be forced to true if all the I/O hook values have been written successfully, or to a false value in case of some write failure.
Write on change can be enabled to perform single write for every I/O hook whose tag change value (or whose value is forced). The Write on change disable can be configured with an expression (normally a single tag) that when non false disable the write on tag changes. This can be useful if a massive tag change is expected and you what to write all tag at once with a Block write.
Poor quality to tag filter: is the time after a bad I/O hook value read after which the tag will be set in a poor quality status.
Alarm only: a flag for Unity import feature only.
Auto I/O hook JavaCode fun.: see JavaCode function provided IOHooks.