38 • Fieldbus coupler/controller Fieldbus controller 750-819
3.2.4 Operating system
3.2.4.1 Start-up
The controller starts-up after switching on the supply voltage or after a hardware reset. The PLC program in the flash memory is transferred to the RAM.
This is followed by the initialization of the system. The controller determines the I/O modules and the present configuration. The variables are set to 0 or to FALSE or to an initialization value given by the PLC program. The flags retain their status . The "I/O" LED blinks red during this phase.
Attention
PFC program variables that are linked with network input variables are also set to 0 or to FALSE after reset, even if they are defined in the retentive memory area or as a flag.
Therefore, variables used for external configuration via LON fieldbus must be linked with CPs (Configuration Properties).
More information
i You can find detailled information on the Configuration Properties (CPs) in Chapter 3.2.6.1 "Memory areas" and Chapter 3.2.6.2.3 "Addressing the configuration variable".
Following an error free start-up, the controller changes over to the "RUN" mode. The "I/O" LED lights up green.
In the delivery state the flash memory is blank therefore no PFC program is included.
Attention
An application program in accordance with IEC 61131-3 is absolutely necessary for the fieldbus controller to operate. The data of the bus modules need to be copyed into the PFC variables (fieldbus variables) via the IEC 61131-3 application program, in order to be used.
Modular I/O System
LONWORKS®
Fieldbus coupler/controller |
• 39 |
Fieldbus controller 750-819 |
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3.2.4.2 PLC cycle
The PLC cycle starts following an error free start-up when the operating mode switch is in the top position or by a start command from the WAGO-I/O-PRO 32. The input and output data of the fieldbus and the I/O modules as well as the times are read. Subsequently the PLC program in the RAM is processed followed by the output data of the fieldbus and the I/O
modules in the process image. Operating system functions, amongst others, for diagnosis and communication are performed and the times are updated at the end of the PLC cycle. The cycle starts again with the reading in of the input and output data and the times.
The change of the operating mode (STOP/RUN) is made at the end of a PLC cycle.
The cycle time is the time from the start of the PLC program to the next start. If a loop is programmed within a PLC program, the PLC running time and thus the PLC cycle are extended correspondingly.
The inputs, outputs and times are not updated during the processing of the PLC program. This update occurs in a defined manner only at the end of the PLC program. For this reason it is not possible to wait for an event from the process or the elapse of a time within a loop.
Modular I/O System
LONWORKS®
40 • Fieldbus coupler/controller Fieldbus controller 750-819
Switching on the supply voltage
Is a PLC
program in the Flash No
memory ?
“I/O” LED
is blinking Yes orange
PLC program transfer from the flash memory to RAM
Determination of the I/O modules and the configuration
Initialization of the system
“I/O” LED is blinking
red No Test o.k.?
Yes
STOP
Operating mode
RUN
PLC cycle
Reading inputs, outputs and times
PLC program in the RAM is processed
“I/O” LED
is shining green
Writing outputs
Operating system functions, updating times
STOP
Operating mode
RUN
Fig. 3-13: Controller operating system
Determination of the I/O modules and the configuration
Variables are set to 0 or FALSE or to their initial value,
flags remain in the same status.
Stop |
No |
Test o.k.? |
|
Yes
operating mode switch is in the top position or start command in WAGO-IO-PRO 32:
Online/Start or Online/Stop
Fieldbus data,
data of I/O modules
Fieldbus start behaviour as a coupler
Fieldbus data,
data of I/O modules
operating mode switch is in the top position or 
start command in WAGO-IO-PRO 32:
Online/Start or Online/Stop
g012941e
Modular I/O System
LONWORKS®