6100 BSC Programming Manual

Writing Applications that Use 6100 BSC
To allow a conversational reply instead of an acknowledgement,
the application makes a WRITEREAD request, instead of a WRITE.
(In this case, the transmitted block normally ends with ETX,
although 6100 BSC does not enforce that restriction.) To make
the reply, the receiving station makes a WRITEREAD request. To
acknowledge the block instead of making a conversational reply,
the station makes a READ request.
Upon receiving a text reply, a station may use a READ request to
send an acknowledgement, as in Figure 3-7. Then the stations
change roles (transmitting <--> receiving) until the next
conversational reply. This is the normal implementation of
limited conversational mode.
If a station receives a text reply and its previous transmission
was not a text reply, it may optionally use a WRITE or WRITEREAD
request, instead of a READ. That is, it may send a message in
answer to a conversational reply, provided that it has not made
more than one conversational reply in a row. Many devices do not
support this extension of conversational mode.
NOTE
The restriction that a station may not send more than one
conversational reply in a row does not apply to the
multileaving option. In multileaving state, applications
exchange WRITEREAD requests exclusively. (A multileaving
station may also issue CONTROL DISCONNECT to disconnect
the line.)
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