S-COM 7K - Synchronizing Messages and Commands

Messages
4-5
program to be sure the controller follows your wishes. Most users expect CW
messages, beeps and perhaps speech messages to be mixed with repeat
audio, since sending them unmixed would mute repeat audio for the duration of
the message. However, pages, announcements, and so forth, may be sent
unmixed to ensure they are received and decoded properly.
Synchronizing Messages and Commands
In the controller, the Message Handler processes messages from the Message
Queue. The Command Executive processes commands and macros from the
Execution Queue. These queues are processed independently but
simultaneously. Messages and commands queued at the same time and
expected to operate in sequence can have unexpected results. That is, unless
you use the message control character to keep everything in synchronization.
Suppose you want to generate a DTMF page of “1234”, then switch on logic
output number 1. You might write a macro with the following commands:
(PW) 20 9000 (PW) 15 9950 01 02 03 04 *
(PW) 29 9000 (PW) 70 1 *
However, this command sequence will not have the expected results. The first
command queues the DTMF page to the message queue for execution then
immediately executes the command to turn on the logic output. The logic
output will change before the DTMF command has completed.
To cause the second line of the macro to wait until after the first line has sent
the DTMF page, you write this as two macros:
(PW) 20 9000 (PW) 15 9950 01 02 03 04 9999 9001 *
(PW) 20 9001 (PW) 70 1 *
“9999” in the macro 9000 is a Message Control Character that causes a macro
to be executed when the Message Handler reaches that point in the message.
The “9001” that follows the 9999 message control character is the name of the
macro to execute. This sequence operates as expected because the DTMF
page will complete before the command to turn on the logic output is executed.
Note: Macro names used with the 9999 Message Control Character must be 4
digits long. Add leading zeros if required.
This type of sequencing also has uses in Autopatch speed dial macros that dial
a pager, then send a DTMF page as the message to be displayed on the
dialed digital pager.