XC2200 Derivatives
System Units (Vol. 1 of 2)
Interrupt and Trap Functions
User’s Manual
5-39
V2.1, 2008-08
ICU_X2K, V2.2
5.9
OCDS Requests
The OCDS module issues high-priority break requests or standard service requests. The
break requests are routed directly to the CPU (like the hardware trap requests) and are
prioritized there. Therefore, break requests ignore the standard interrupt arbitration and
receive highest priority.
The standard OCDS service requests are routed to the CPU Action Control Unit together
with the arbitrated interrupt/PEC requests. The service request with the higher priority is
sent to the CPU to be serviced. If both the interrupt/PEC request and the OCDS request
have the same priority level, the interrupt/PEC request wins.
This approach ensures precise break control, while affecting the system behavior as little
as possible.
The CPU Action Control Unit also routes back request acknowledges and denials from
the core to the corresponding requestor.