GDSX Manual

LINE^HANDLER Example, Design
Extended General Device Support (GDSX) Manual–134303
7-5
Intertask Communication—LINE^HANDLER
Perspective
When the WAIT^EVENT procedure is called, control is transferred to TSCODE, which
checks to see whether certain events have occurred. The events checked for are
specified in a bit-encoded mask passed to TSCODE along with a timeout parameter.
When one of these specified events occurs, TSCODE returns an indicator of the event
type.
The event descriptions and the global literals (declared in DCCBDECS (EVENTS))
used by TSCODE to define the events are given in Table 7-1. Events having an IOCB
associated with them are marked in the fourth column.
Figure 7-2. Sending a WRITEREAD Through a LINE^HANDLER (page 2 of 2)
Data goes to
the IOP and is
sent to the
terminal (line).
The L^H task detects the intertask
request and then issues a
^WRITEREAD to send the data to the
terminal (line).
The L^H task can continue to process
other requests, but checks for the I/O
completion event.
TSCODE receives the I/O completion message, identifies which L^H task the
message is for, and uses WAKE^TASK to pass it to the L^H task for processing.
The L^H task locates the IOCB
belonging to the original request and
calls NOTIFY^IO^COMPLETION.
NOTIFY^IO^COMPLETION causes TSCODE to execute a
WAKE^TASK and pass the information on to the D^H task.
The D^H task sends a response to
the application by calling ^REPLY.
Requester
receives
response.
Application D^H Task L^H Task IOP/Terminal
The I/O
completion
message is
sent.
CDT142