• Next sequential address: In the absence of other instructions, the control unit’s
control address register is incremented by 1.
• Opcode mapping: At the beginning of each instruction cycle, the next microinstruction
address is determined by the opcode.
• Subroutine facility: Explained presently.
• Interrupt testing: Certain microinstructions specify a test for interrupts. If an
interrupt has occurred, this determines the next microinstruction address.
• Branch: Conditional and unconditional branch microinstructions are used.