Method to minimize the number of IRQ lines from peripherals to one wire

A method operational on a master device, comprising:

• grouping slave devices coupled to a shared single line interrupt request (IRQ) bus into one or more groups, where each group is associated with a different IRQ signal;
• monitoring the IRQ bus to ascertain when an IRQ signal is asserted by one or more of the slave devices;
• when two or more slave devices have asserted the IRQ signal concurrently on a same wire, selecting for interrupt service a group with which the at least one of the two or more devices is associated based on duration of assertion of the IRQ signal;
• and
• scanning at least one slave device in the identified group to ascertain an asserting slave device that asserted the IRQ signal on the IRQ bus, wherein each of the slave devices is configured to unilaterally drive the IRQ bus asynchronously with respect to the master device.

A slave device, comprising:

• a first interface to a single line interrupt request (IRQ) bus to which a master device is coupled, wherein the slave device is configured to unilaterally drive the IRQ bus asynchronously with respect to the master device;
• a second interface to a control data bus to which the master device is also coupled;
• and
• a processing circuit coupled to the first interface and the second interface, the processing circuit adapted to:
• obtain a group assignment from a master device, wherein the group assignment identifies one group from a plurality of groups, each group being associated with a different IRQ signal;
• monitor the IRQ bus to ascertain whether an IRQ signal is asserted by another slave device;
• and
• assert a first IRQ signal on the IRQ bus when no other IRQ signal is asserted on the IRQ bus.

A method operational on a slave device, comprising:

• obtaining a group assignment from a master device, wherein the group assignment identifies one group from a plurality of groups, each group being associated with a different interrupt request (IRQ) signal;
• monitoring a single line IRQ bus to ascertain whether an IRQ signal is asserted by a different slave device;
• and
• asserting a first IRQ signal on the IRQ bus when no other IRQ signal is asserted on the IRQ bus, wherein the slave device is configured to unilaterally drive the IRQ bus asynchronously with respect to the master device.

A master device, comprising:

• a first interface to a single line interrupt request (IRQ) bus to which one or more slave devices are coupled;
• a second interface to a serial data bus to which the one or more slave devices are also coupled;
• and
• a processing circuit coupled to the first interface and the second interface, the processing circuit adapted to:
• group the one or more slave devices into one or more groups, where each group is associated with a different IRQ signal;
• monitor the first interface to ascertain when an IRQ signal is asserted by at least one slave device;
• identify a group with which the IRQ signal is associated;
• and
• scan the slave devices of the identified group to ascertain an asserting slave device which asserted the IRQ signal on the IRQ bus, wherein each of the slave devices is configured to unilaterally drive the IRQ bus asynchronously with respect to the master device,
• wherein each of the one or more slave devices coupled to the serial data bus is configured to assert the IRQ signal on the IRQ bus after confirming that the IRQ bus is idle.

A slave device, comprising:

• a first interface to a single line interrupt request (IRQ) bus to which a master device is coupled, wherein the slave device is configured to unilaterally drive the IRQ bus asynchronously with respect to the master device;
• a second interface to a serial data bus to which the master device is also coupled;
• and
• a processing circuit coupled to the first interface and the second interface, the processing circuit adapted to:
• determining a group assignment for the slave device, wherein the group assignment identifies one group from a plurality of groups, each group being associated with a different IRQ signal;
• confirm that the IRQ bus is idle;
• and
• assert a first IRQ signal after confirming that the IRQ bus is idle.