DHQ1ECCSECETS1SR1WH View Datasheet(PDF) - Intel

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Description

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DHQ1ECCSECETS1SR1WH

Intel® Quark SoC X1000

Intel 

Intel® Quark SoC X1000—Legacy Bridge

21.12.1.3 Operation Command Words (OCW)

These command words reprogram the Interrupt controller to operate in various

interrupt modes.

• OCW1 masks and unmasks interrupt lines.

• OCW2 controls the rotation of interrupt priorities when in rotating priority mode,

and controls the EOI function.

• OCW3 sets up ISR/IRR reads, enables/disables the special mask mode (SMM), and

enables/disables polled interrupt mode.

21.12.1.4 Modes of Operation

21.12.1.4.1 Fully Nested Mode

In this mode, interrupt requests are ordered in priority from 0 through 7, with 0 being

the highest. When an interrupt is acknowledged, the highest priority request is

determined and its vector placed on the bus. Additionally, the ISR for the interrupt is

set. This ISR bit remains set until either: the processor issues an EOI command

immediately before returning from the service routine; or if in AEOI mode, on the

trailing edge of the second INTA#. While the ISR bit is set, all further interrupts of the

same or lower priority are inhibited, while higher levels generate another interrupt.

Interrupt priorities can be changed in the rotating priority mode.

21.12.1.4.2 Special Fully-Nested Mode

This mode is used in the case of a system where cascading is used, and the priority has

to be conserved within each slave. In this case, the special fully-nested mode is

programmed to the master controller. This mode is similar to the fully-nested mode

with the following exceptions:

• When an interrupt request from a certain slave is in service, this slave is not locked

out from the master's priority logic and further interrupt requests from higher

priority interrupts within the slave are recognized by the master and initiate

interrupts to the processor. In the normal-nested mode, a slave is masked out

when its request is in service.

• When exiting the Interrupt Service routine, software has to check whether the

interrupt serviced was the only one from that slave. This is done by sending a non-

Specific EOI command to the slave and then reading its ISR. If it is 0, a non-

specific EOI can also be sent to the master.

21.12.1.4.3 Automatic Rotation Mode (Equal Priority Devices)

In some applications, there are a number of interrupting devices of equal priority.

Automatic rotation mode provides for a sequential 8-way rotation. In this mode, a

device receives the lowest priority after being serviced. In the worst case, a device

requesting an interrupt has to wait until each of seven other devices are serviced at

most once.

There are two ways to accomplish automatic rotation using OCW2.REOI; the Rotation

on Non-Specific EOI Command (OCW2.REOI=101b) and the rotate in automatic EOI

mode which is set by (OCW2.REOI=100b).

Intel® Quark SoC X1000

DS

888

October 2013

Document Number: 329676-001US

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