BECKHOFF C1220 User Manual

Page 26

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Software description of functions

Beckhoff Lightbus - PC interface card C1220

If the PC modifies this mask, it is inserted into the interrupt fields of the
next telegrams. The nibble is inserted into the interrupt field until it is
withdrawn again by the PC.

IRQ inputs:

II3

II2

II1

II0

If an address-independent interrupt is generated by an I/O module, it is
transferred to the PC via this mask provided it is enabled by the interrupt
mask.

Pending interrupts are buffered by the C1220, i.e. only ever one interrupt is
transferred the PC via the GCB. Any other pending interrupt is not
transferred until this one has been recognized by the PC.

Control mask:

Bit C0 can be used to allow the PC to switch off the resident address test,
or to reactivate it. In order to be able to localise parity errors, the address
check must be active.

C0 set

: Address test active.

C1 reset

: Address test active even with optical fibre errors.

C0 is set by default.