6100 ADCCP Programming Manual

Link States and Transitions
ADCCP Link and Station Management
2–4 069225 Tandem Computers Incorporated
Figure 2-2. Input Frame Handling
7
008
Legend
The frame arrives, and the driver receives it.
Level 1 checks the address and passes the frame to Level 2.
Level 2 queues a response frame for Level 1.
Level 1 prepares the response frame for transmission.
The driver puts the response frame on the line.
Level 2 informs the Protocol Manager.
The Protocol Manager completes an outstanding request.
DriverLevel 1
Link
Manager
Level 2
Station
Manager
Protocol
Manager
Frame
Response
Line
123
4 56
1
2
3
4
5
6
7
Link States and
Transitions
The Level 1 Protocol functions as a “state machine.” At any given time, the link is in
one of four states:
DISC^IDLE
DISC^WAIT
READY^IDLE
XMIT
Application requests and arriving frames are “events” that may change the state of the
link. Only certain events make sense for each state. For example, an application
cannot send data if the link is disconnected.
Figure 2-3 shows the major link states and the events that cause state transitions.