6100 BSC Programming Manual

Writing Applications that Use 6100 BSC
WRITEREAD Request and Response
The WRITEREAD request has several major functions, depending
on the line state:
• If the state is DISCONNECTED, the WRITEREAD request
implicitly connects the station. The same request can
accomplish ID exchange, or it can make a line bid,
send the first block, and receive an acknowledgement or
conversational reply.
• If the state is CIRCUIT ASSURANCE, the WRITEREAD request
transmits the ID of the calling station, and reads the ID of
the called station. If this is the called station, the
WRITEREAD request transmits the ID of the called station, and
reads the response (which might be a line bid.)
• If the state is CONTROL, the WRITEREAD request makes a line
bid, sends the first message or block, and accepts an
acknowledgement or conversational reply. To allow a
conversational reply, the block should end in ETX, e.g., it
should be the last block of a message. (BSC does not enforce
this restriction.)
• If the state is WRITE, the WRITEREAD request sends a message
or block, and accepts an acknowledgement or a conversational
reply.
• If the state is READ, the WRITEREAD request sends a
conversational reply and accepts either an acknowledgement or
another message.
• If the state is MULTILEAVING, the WRITEREAD request sends
data to the remote station and accepts a reply.
The WRITEREAD request completes when the transmission has been
acknowledged or when the remote station has made a conversational
reply.
Each use of WRITEREAD has been discussed and illustrated in this
section.
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