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GT-96100A Advanced Communication Controller
426
Revision 1.0
21.3
Interrupt Summaries
The GT-96100A provides the following three interrupt summary bits in the main cause register:
IntSum (bit [0] in the Main_Cause register) is the logical OR of all interrupt bits in both the
Main_Cause and High_Cause registers. This OR is not affected by the state of the mask bits and can be
used for event polling.
Int0*Sum (bit [30] in the Main_Cause register) is the logical OR of all interrupt bits in both the
Main_Cause and High_Cause registers masked by Interrupt0* mask registers. It serves as an indication
that at least one of the (unmasked) Interrupt0* events is set.
Int1*Sum (bit [31] in the Main_Cause register) is the logical OR of all interrupt bits in both the
Main_Cause and High_Cause registers masked by Interrupt1* mask registers. It serves as an indication
that at least one of the (unmasked) Interrupt1* events is set.
21.4
Interrupt Select Registers
There are two interrupt select registers that can be used to optimize interrupt service routines. One select register
is associated with Interrupt0* (offset 0x000C70) and another register is associated with interrupt1* (offset
0x000C74).
These select registers optimize service routines is the following manner:
Instead of checking BOTH the Main_Cause register and the High_Cause register, when interrupted, the
CPU has the option to read the appropriate select register.
The select register will reflect the Cause register bits of either the Main_Cause or the High_Cause regis-
ters, depending on which register has active unmasked interrupt bits.
Bit [30] of the select register indicates which of the cause registers (Main or High) is selected and bits
[29:0] reflect the state of the interrupt bits of the selected cause register. For example, if bit [5] of the
High_Cause register is set (and is unmasked), and no (unmasked) bit in the Main_Cause register is set,
then bit [5] of the select register is set as well. In addition, bit [30] of the select register is set, indicating
that the High_Cause register is currently being selected.
In case both the Main_Cause and the High_Cause registers have interrupt bits set, the select register reflects the
state of the Main_Cause register (and bit [30] is therefore reset). However, in order to indicate that both cause
registers are active, bit [31] of the select register is also set, in this case.