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The full-duplex protocol conforms closely to ANSI X3.28, combining
features of subcategories D1 (data transparency) and F1 (two-way
simultaneous transmission with embedded responses).
You can use full-duplex protocol for a point-to-point link that allows
two-way simultaneous transmission. It is relatively difficult to implement
because it requires you to use interrupts and multi-tasking programming
techniques. It is intended for high performance applications where you
need to get the highest possible throughput from the available
communication medium.
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Half-duplex protocol serves as an alternate to full-duplex protocol.
Half-duplex protocol is similar to full-duplex in most respects. Two major
differences are:
Half-duplex protocol provides for polling of slave stations.
Half-duplex protocol does not allow embedded responses.
Half-duplex protocol is used for a link between one master and one or
more slaves. You must use modems for this type of link (unless there is
only one slave). The 1785-KE module has slave mode capability only. You
must provide the master function through a computer, or the 1771-KGM
module.
Half-duplex protocol provides a lower effective utilization of resources
compared to full-duplex, but it is easier to implement. You should use
half-duplex protocol if:
you are using multidrop modems to connect multiple slave stations to a
single master computer.
you are using moderns that have only half-duplex capability.
you are willing to sacrifice data throughput in exchange for ease of
implementation.