Datasheet

169

11011B–ATARM–21-Feb-12

SAM3N

• RETTOBASE

Indicates whether there are preempted active exceptions:

0 = there are preempted active exceptions to execute

1 = there are no active exceptions, or the currently-executing exception is the only active exception.

• VECTACTIVE

Contains the active exception number:

0 = Thread mode

Nonzero = The exception number

(1)

of the currently active exception.

Subtract 16 from this value to obtain the IRQ number required to index into the Interrupt Clear-Enable, Set-Enable, Clear-

Pending, Set-Pending, or Priority Registers, see “Interrupt Program Status Register” on page 48.

When you write to the ICSR, the effect is Unpredictable if you:

• write 1 to the PENDSVSET bit and write 1 to the PENDSVCLR bit

• write 1 to the PENDSTSET bit and write 1 to the PENDSTCLR bit.

Note: 1. This is the same value as IPSR bits [8:0] see “Interrupt Program Status Register” on page 48.