Texas Instruments 990 User Manual page 219

Throughput
T2-Tl is the poll transmission time.
T3-T2 is the time required for the secondary to process the
input and formulate a data link level response (TAT).
T4-T3 is the response transmission time.
T5-T4 is the FCCC poller program response processing time.
During time TI-TO, the FCCC performs such functions as the
following:
*
*
*
*
Chains to the next station control block and tests to
see if there is time to poll. If there is not enough
time, it chains to the next station control block.
Acquires an input communications buffer and associates
it with the output poll. If no buffer is available, it
sets appropriate flags and prepares to send a negative
poll.
Gets HDLe sequence counts and builds the poll command.
Sets appropriate
output call.
flags
and counters and performs an
During time T3-T2, the secondary station performs such functions
as the following:
*
Processes input,characters.
*
Tests the input poll for validity and directive.
*
Validity checking tests the poll type and sequence
counts for validity. Directive checking tests the poll
type to determine if the secondary response can include
a message.
Processes and begins transfer of response.
During time T5-T4, the poller processes the response to the poll
by performing the following:
*
Tests the input (response) for presence of message.
*
Tests HDLC sequence counts regardless of response type.
*
Performs any flag and counting operations required to
finalize the poll sequence.
*
Returns to the logic to begin the chaining operation
through the station control blocks.
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