6100 BSC Programming Manual

6100 BSC Link and Station Management
READ State
A station is in READ state when reading text, and whenever it
owes an acknowledgement to the other station, i.e., between
READ requests.
TRANSITIONS TO READ STATE. The following requests cause a
station to be in READ state:
• The application makes a READ request to accept a line bid and
read the first message. The state changes from CONTROL to
READ. During the series of READ requests, the receiving
station stays in READ state most of the time.
• The application makes a WRITEREAD request to transmit a
message and accept a conversational reply. The station is in
WRITE state while transmitting the message, but it changes
to READ state if it accepts a conversational reply. By
using a READ request to send an acknowledgement, the station
enters READ state; by using a WRITE request to send a text
reply, the station remains in WRITE state.
TRANSITIONS FROM READ STATE. Transitions from READ state to
other states occur during every protocol transaction. The
following events leave a station in some other state upon their
completion:
• The application makes a WRITEREAD request to send a
conversational reply. Although the station was in READ state
before the WRITEREAD request, it may change role when it sends
the conversational reply. If the other station responds with
an ACK 0 or ACK 1, the line state changes to WRITE; if the
other station responds with text, the line state continues to
be READ.
• The application or the remote station sends an EOT sequence.
The state changes to CONTROL.
• The application or the remote station sends a disconnect
sequence (DLE EOT), a modem failure causes DSR to drop, or the
application makes a STOP request. The state changes to
DISCONNECTED; BSC reports an error to the application.
• The retry count is exhausted on either a READ request or the
READ part of a WRITEREAD. The corresponding status codes are
162, 163, 172, 173, 175, and 177. (See Section 3 for
descriptions of the errors.) The state changes to CONTROL.
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