Intel 8XC196MC manual Special Operating Mode Signals and Registers, Operating Mode Control Signals

CHAPTER 14

SPECIAL OPERATING MODES

The 8XC196MC, MD, and MH provide two power saving modes: idle and powerdown. They also provide an on-circuit emulation (ONCE) mode that electrically isolates the device from the other system components. This chapter describes each mode and explains how to enter and exit each. (Refer to Appendix A for descriptions of the instructions discussed in this chapter, to Ap- pendix B for descriptions of signal status during each mode, and to Appendix C for details about the registers.)

14.1 SPECIAL OPERATING MODE SIGNALS AND REGISTERS

Table 14-1 lists the signals and Table 14-2 lists the registers that are mentioned in this chapter.

Table 14-1. Operating Mode Control Signals

Port Pin	Signal	Type	Description
	Name
P2.7	CLKOUT	O	Clock Output
	(MC/MD		Output of the internal clock generator. The CLKOUT frequency is ½
	only)
			the oscillator input frequency (FXTAL1). CLKOUT has a 50% duty cycle.
			CLKOUT is not implemented on the 8XC196MH.
—	EXTINT	I	External Interrupt
			This programmable interrupt is controlled by the WG_PROTECT
			register. This register controls whether the interrupt is edge triggered
			or sampled and whether a rising edge/high level or falling edge/low
			level activates the interrupt.
			In powerdown mode, asserting the EXTINT signal for at least 50 ns
			causes the device to resume normal operation. The interrupt need not
			be enabled. If the EXTINT interrupt is enabled, the CPU executes the
			interrupt service routine. Otherwise, the CPU executes the instruction
			that immediately follows the command that invoked the power-saving
			mode.
			In idle mode, asserting any enabled interrupt causes the device to
			resume normal operation.

14-1