Envoy Configuration and Management Manual

Introduction to Envoy
Envoy Configuration and Management Manual—429861-001
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Envoy Lines and Line-Handler Processes
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Conversion of ASCII code to EBCDIC code, and EBCDIC to ASCII
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Automatic polling of multipoint tributary stations
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Point-to-point or multipoint transmission modes
Multipoint Polling
In Envoy multipoint configurations, the ServerNet WAN concentrator also handles some
polling functions.
When used as the supervisor station, the ServerNet WAN concentrator manages the
polling of the lines. Envoy passes a polling list created by the user to the WAN
subsystem, and polling begins. (See the Envoy Application Programming Manual for
further information on polling.)
The ServerNet WAN concentrator is interrupted when text is received from a polled
station, when polling is stopped, or when the poll list is exhausted.
When used as a tributary station, the ServerNet WAN concentrator recognizes when its
lines are polled or selected. For each line, Envoy stores up to two distinct secondary
addresses. Envoy uses incoming frames containing the specified addresses to satisfy
outstanding read requests and discards other frames.
EBCDIC Translation
The WAN subsystem’s internal character code is always ASCII. However, you can
configure the line characteristics to translate to EBCDIC (on output) and from EBCDIC
(on input) for communicating with an EBCDIC-based computer.
Refer to the Envoy Application Programming Manual for the ASCII character set and an
ASCII to EBCDIC code conversion table.
Electrical Interfaces
The following electrical interfaces are available with the ServerNet WAN concentrator:
RS-232
RS-422
Envoy Lines and Line-Handler Processes
Each Envoy line has an associated line-handler process; that is, there is a one-to-one
correspondence between Envoy lines and Envoy line-handler processes. To add an
Envoy line, you add an Envoy line-handler process object; a corresponding LINE object
is defined automatically.