In VME the AORTA-R has been equipped with a set of 16 programmable interrupt vectors; every control character is mapped onto one of these interrupt vectors; just like the data item counter values interrupt vectors are stored in a FIFO (2Kx8 bit) so that all generated interrupts are accumulated and handled in the proper (=chronological) order.
When a control character is received the data item counter value is entered into the counter FIFO and the interrupt vector corresponding to this control character is entered into the vector FIFO (if this particular interrupt is enabled); as long as the vector FIFO is not empty an interrupt is present on the VME-bus; at a VME interrupt acknowledge cycle a vector value is taken from the vector FIFO and returned to the VME master.
Table 1 lists the control characters, their usage by the HOTLink chips and their mapping on the 16 programmable VME interrupt vectors (here numbered from 0 to 15).
Table: Control characters ('CChar'), their usage by the HOTLink chips,
and the mapping on the 16 AORTA-R-V2 VME control-char interrupt
numbers. (C-SOF=Connect-Start-Of-Frame, P-SOF=Passive-Start-Of-Frame).