5
Diagnostics and error handling
52
Festo – P.BE-CPX-CTEL-EN – 1411a – English
After an interruption is determined, the relevant I-port is queried cyclically and checked for a connec
tion-capable device.
If a device is recognised, the following procedures are possible:
The recognised device agrees with the manual configuration (I/Os and I/O lengths).
The system can continue to be operated without limitation.
If the I/O length of the recognised device is less than the length established in manual
configuration, the I/O bytes used are assigned to the “lower end” of the reserved address
space in the CPX system.
The unassigned bytes at the “upper end” remain unused.
Example:
Manual configuration with an I/O length of 8 bytes. A device with an I/O length of 4 bytes is connected.
The 4 bytes of the device are assigned to the first 4 bytes in the address space of the I-port. The re
maining 4 bytes remain unused.
I-Port
Fixed I/O length 8 bytes
Device: 4 bytes
I-Port
Byte 0
Byte 0
Byte 1
Byte 1
Byte 2
Byte 2
Byte 3
Byte 3
Byte 4
X
Byte 5
X
Byte 6
X
Byte 7
X
Tab. 5.5
The recognised device has established a larger I/O length than in the manual configuration.
The system can still be operated. But the I/O bytes that “project” beyond the reserved address space
are ignored.
Example:
Manual configuration with an I/O length of 4 bytes. Connected is a device with an I/O length of 8 bytes.
The first 4 bytes of the device are assigned to the 4 bytes in the address space of the I-port. The re
maining 4 bytes of the device remain unused.
I-Port
Fixed I/O length 4 bytes
Device: 8 bytes
I-Port
Byte 0
Byte 0
Byte 1
Byte 1
Byte 2
Byte 2
Byte 3
Byte 3
X
Byte 4
X
Byte 5
X
Byte 6
X
Byte 7
Tab. 5.6
Summary of Contents for CPX-FB13
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