Intel NETWORK PROCESSOR IXP2800 - Manual (Page 132)

132 Hardware Reference Manual
Intel
®
IXP2800 Network Processor
Intel XScale ® Core
3.11.8 Interrupt
The Intel XScale
®
core CSR controller contains local CSR(s) and interrupts inputs from multiple
sources. The diagram in Figure 28 shows the flow through the controller.
Within the Interrupt/CSR register block there are raw status registers, enable registers, and local
CSR(s). The raw status registers are the un-masked interrupt status. These interrupt status are
masked or steered to theIntel XScale
® core’s IRQ or FIQ inputs by multiple levels of enable
registers.
Refer to Figure 29 .
• {IRQ,FIQ}Status = (RawStatus & {IRQ,FIQ}Enable)
• {IRQ,FIQ}ErrorStatus = (ErrorRawStatus & {IRQ,FIQ}ErrorEnable)
• {IRQ,FIQ}ThreadStatus_$_# = ({IRQ,FIQ}ThreadRawStatus_$_# &
{IRQ,FIQ}ThreadEnable_$_#)
Each interrupt input is visible in the RawStatus register and is masked or steered by two level of
interrupt enable registers. The error and thread status are masked by one level of enable registers.
Their combination along with other interrupt sources contributes to the RawStatusReg. The
RawStatus is masked via IRQEnable/FIQEnable to trigger the IRQ and FIQ interrupt to the Intel
XScale
®
core.
The enable register’s bits are set and cleared through EnableSet and EnableClear registers. The
Status, RawStatus, and Enable registers are read-only, and EnableSet and EnableClear are
write-only. Also, Enable and EnableSet share the same address for reads and writes respectively.
Note that software needs to take into account the delay between the clearing of an interrupt
condition and having its status updated in the RawStatus registers. Also in the case of simultaneous
writes to the same registers, the value of the last write is recorded.
Figure 28. Flow Through the Intel XScale ® Core Interrupt Controller
A9698-01
CAP_CSR_WR_ADDR
CAP_CSR_WR
From cbiAdr
From cbiData
cbrData
FIQ IRQ
CAP_CSR_WR_DATA
CSR
Decode
Interrupt/
CSR
Registers