User Manual M3000® Automation System / MSC II (Moog Servo ...

7 Networking M3000 ® Modules E-Bus
7.6.3.2 Update Rate of E-Bus Messages
WARNING The I/O extension modules QDIO and QAIO monitor the
E-bus activity and disable their outputs if they do not receive
an E-bus message more frequently than 50 ms.
To avoid this, set the value of the system basetick or the
value of 'UpdateRate' so that the product of the two values is
less than 50 ms.
The update rate setting of the E-bus depends on the system basetick. The
system basetick is the time base for the operating system tasks, used in the
application program. Task time bases of tasks can be set to integer multiples
of the system basetick.
The update rate is defined by setting the E-bus module parameter 'Update-
Rate' in the PLC configuration of the MACS development environment.
'UpdateRate' can be set so that an E-bus message will always be sent at the
end of this task's cycle (or after 2, 3, 5, 10, 15 or 20 cycles).
MSC II Module
Parameter
'Basetick'
E-Bus Module Parameter
'UpdateRate' Update Rate of E-Bus Messages
1 ms 'every third cycle' An E-bus message is started cyclically every
3 ms (1 ms * 3).
3 ms 'every twentieth cycle' An E-bus message would be started cyclically
every 60 ms (3 ms * 20).
However, since no E-bus message is sent
more frequently than 50 ms, the I/O extension
modules will disable their outputs. The outputs
will be re-enabled with the next E-bus
message.
Table 13: Update Rate of E-Bus Messages
7.6.3.3 Duration of Transmission of E-Bus Messages
The duration of transmission of the E-bus message, i.e., the length of time required
to transmit the E-bus message, is determined by the E-bus clock frequency.
The E-bus clock frequency is defined by setting the E-bus module
parameter 'Frequency' in the PLC configuration of the MACS development
environment.
• Clock frequency = 10 MHz � Duration of transmission = 42 µs
• Clock frequency = 5 MHz � Duration of transmission = 84 µs
The selected E-bus clock frequency does not influence the time required to
execute the tasks.
When the E-bus group contains QAIOs 16/4, the clock frequency must
be set to 5 MHz!
When the E-bus group contains QAIOs 2/2, the clock frequency must be
set to 10 MHz!
The duration of transmission of E-bus messages is not influenced by the
number of DIN rail modules in the E-bus group.
E-Bus Communication:
Message Update Rate
E-Bus Communication:
Duration of Message
Transmission
© Moog GmbH User Manual M3000 ® and MSC II (CA65865-001; Version 1.1, 08/08) 62