The event fabric has two types of registers.
The first type, a configuration register, is used to control and report the selection
settings for a subscriber output. For each subscriber output, an address is mapped for a
read register that contains a value representing the selection of the input event
currently set for that subscriber output. For non-configurable outputs, only a read-only
register is implemented. A read to that address returns the static, predefined value.
The second type of register in the event fabric are description registers and one
register that can be used for observation of event signals on the pads.