XC2200 Derivatives
System Units (Vol. 1 of 2)
The External Bus Controller EBC
User’s Manual
9-25
V2.1, 2008-08
EBC_X8, V1.0d1
9.3.6.3
Address Window Arbitration
For each external access the EBC compares the current address with all address select
registers (programmable ADDRSELx and hard wired address select registers for startup
memory) of enabled windows. This comparison is done in four levels:
Priority 1:
Registers ADDRSELx [x = 2, 4] are evaluated first. A window match with one of these
registers directs the access to the respective external area using the corresponding set
of control registers FCONCSx/TCONCSx and ignoring registers ADDRSELy. An
overlapping of windows of this group will lead to an undefined behaviour.
Priority 2:
A match with registers ADDRSELy [y = 1, 3, 7] directs the access to the respective
external area using the corresponding set of control registers FCONCSy/TCONCSy. An
overlapping of windows of this group will lead to an undefined behaviour. Overlaps with
priority 2 ADDRSELx are only allowed for the (x, y) pairs (2, 1) and (4, 3).
Priority 3:
If there is no match with any address select register (neither the hardware ones nor the
programmable ADDRSEL) the access to the external bus uses the general set of control
registers FCONCS0/TCONCS0 if enabled.
