Sullair Supervisor 2 Deluxe, Руководство оператора

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Section 6
SUPERVISOR PROTOCOL
machine assigned to that time slot is off line and the next time slot starts.
A machine sends a net status message immediately after a message is received from the
next previous machine, or that machine’s time slot has expired. For example if the time slot
has been established as 2 and either machine 2 sends a net status message or no mes-
sage is sent within .125 seconds, then machine 3 will send a net status message (if on line).
During time slot 0 a monitor may send a message, typically a status request or parameter
change message. A message that is sent by the monitor may need a response from one of
the machines. This response must come before the time out period (.5 sec).
Consider the following system with 4 machines with no monitor and machine 3 is off line.
Time Slot COM ID# Status Action
0 Monitor Off line .5 sec time out
1 1 On line Machine 1
net message
2 2 On line Machine 2 net
message
3 3 Off line .125 sec time out
4 4 On line Machine 4 net
message
Let’s start this example at time slot 1. Machine 1 sends a net message. Machine 2 receives
the message and establishes the time slot as 2. Machine 2 immediately sends its net sta-
tus message establishing the slot at 3. Since machine 3 is off line no message will be sent
and after .125 sec. the time slot will rotate to 4. Machine 4 will send it’s net status message,
and the time slot will roll over to slot 0. Since there is no monitor, after .5 sec. the time slot
will rotate to 1 and machine 1 will send it’s net status message. This cycle will repeat until
other machines go off or on line. When a machine is switched on line or powered up it does
not know what the time slot is until it receives a net message from another machine. If only
one machine is put on line, or multiple machines are powered up at the same time, none of
them will know what the current time slot is. To overcome this deadlock the following
scheme is used.
When a machine comes on line it waits for an initial timeout period of 1.5 seconds times its
COM ID#. For example if it’s COM ID# is 4 then it will wait 6 seconds. If a message is
received during the initial timeout period then the time slot will be known because the
sender’s COM ID# is embedded in the message. For example if a net message from
machine 2 is received then the time slot is 2.
If no messages are received within the initial timeout period then a net message is sent. It
can be assumed that either there are no other machines on line or that they have been put
on line at the same time and are waiting for their initial timeout to expire. This keeps sever-
al machines that are powered up at the same time from all sending net status messages
simultaneously.