External Ports


To understand the use of External Ports, it is probably better to read the sections on Ports and Subnets first.  External Ports indicate the ports of a subnet, and basically just have a name, which must match a subnet port name at the next higher level.

An External Port can be one of three types: input, output and output/input. 

The output/input external port is really an output type linked tightly to an input type, and therefore must have two names associated with it.
 

Right clicking on an External Port brings up a popup menu showing operations that can be performed on it.  These are the following:

An External Port can be connected by arrows to any block type - see the section on Arrows.  However, arrows in some directions are prevented by the diagramming tool, e.g. routing an arrow from a block to an input-type external port is forbidden.

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In the case of the output/input type, the two associated names are entered together, but separated by a colon, as follows:

ABC:DEF