Texas Instruments 990 User Manual page 47

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Operating in command file mode requires anticipating all of the transactions for the duratioq of
command file mode. The command file must include the same commands that would be use'a in
operator mode. Because the operator cannot change the command file commands whilt ..
~he
command file is executing. the Emulator provides two commands that give the command gotne
decision-making capabilities. The IF and WAIT commands are used by command files to provide
the command file with some of the versatility of an operator.·
The IF command is used in an IF-SELSE-SEND structure to allow the command foe to
conditionally execute or skip a group of its commands. When the specified condition is true, the
Emulator executes all commands until SELSE is encountered in the command stream.then skips all
commands until SEND is encountered. If the specified condition is false, the Emulator skips all
commands until SELSE or SEND is encountered. SELSE and SEND are entered as commands.
Nested IF commands are not allowed. If a second IF command is encountered anywhere within
the original IF-SELSE-SEND structure, it is treated as an invalid command, the message
•••INV AUD INPUT is logged, and execution continues with the next command.
The WAIT command allows the command file to wait until a condition is satisfied before executing
the next command. This is panicularly helpful when the next command depends on the previous
command for its input. The WAIT will wait for a connection, a disconnection, a queue to become
empty, or all queues to become empty. The WAIT command has cenain safeguards built into it to
prevent the command file from waiting indefinitely for a condition that will never be satisfied. These
safeguards arc:
• For a wait until connect
complet~.
the WAIT will be executed only if the Emulator is in a
condition in which connection can be accomplished, e.g., a CALL or ANS command has
been issued prior to the WAIT command.
• For a wah until queue empty, the WAIT will be executed only if a connection has been
established so that it is possible for those queues to go empty.
Once a command file has been executed, the user cannot interrupt the operation of the Emulator
(unless he physically disconnects the connection or kills the task). For this reason, it is important that
care be exercised in arranging the command file. The following suggestions should help avoid
problems. ·
• Make sure that the directory of a multilevel pathname is available or, if it is not, that a
d!=fault pathname is specified.
• Make sure that the number of transactions queued prior to issuing a CALL command do
not exceed the queue buffer space. If this happens, the Emulator waits for queue buffer
space to be available; but without a connection, no buffer space can become available.
A command file may be specified as the primary command source or the secondary command
source. The command file operation is almost the same in either case. The primary difference is that
as a primary command source the command file can issue a CF command to execute a second
command file. The secondary command file issues its commands and then execution returns to the
primary command source. When a secondary command file issues a CF command, the secondary
command file is closed and the newly specified command file begins execution. When the command
file ends, execution returns to the primary. command source, not to the secondary command file.
Digital Systems Group