SETUSR     Set User Mode     Rabbit 3000A/4000 Instruction

Opcode	Instruction	Clocks	Operation
ED 6F	SETUSR	4 (2,2)	SU={SU[5:0],0x01}

Flags				ALTD			IOI/IOE
S	Z	L/V	C	F	R	SP	S	D
-	-	-	-

Description

The System/User Mode Register, SU, is an 8-bit register that forms a stack of the current processor mode and the previous 3 modes. SETUSR shifts the contents of SU 2 bits to the left, then sets bit 1 to 0 and bit 0 to 1, signifying user mode.

This is a chained-atomic instruction, meaning that an interrupt cannot take place between this instruction and the instruction following it.