Intel 8XC196NP manual Unused Inputs, 11.1.2 I/O Port Pin Connections, I/O Port Configuration Guide

8XC196NP, 80C196NU USER’S MANUAL

		Table 11-1. Minimum Required Signals (Continued)
Signal	Type	Description
Name
XTAL1	I	Input Crystal/Resonator or External Clock Input
		Input to the on-chip oscillator, internal phase-locked loop circuitry (80C196NU), and
		the internal clock generators. The internal clock generators provide the peripheral
		clocks, CPU clock, and CLKOUT signal. When using an external clock source
		instead of the on-chip oscillator, connect the clock input to XTAL1. The external
		clock signal must meet the VIH specification for XTAL1 (see datasheet).
XTAL2	O	Inverted Output for the Crystal/Resonator
		Output of the on-chip oscillator inverter. Leave XTAL2 floating when the design uses
		a external clock source instead of the on-chip oscillator.

11.1.1 Unused Inputs

For predictable performance, it is important to tie unused inputs to VCC or VSS. Otherwise, they can float to a mid-voltage level and draw excessive current. Unused interrupt inputs may generate spurious interrupts if left unconnected.

11.1.2 I/O Port Pin Connections

Chapter 7, “I/O Ports,” contains information about initializing and configuring the ports. Table 11-2 lists the sections, with page numbers, that contain the information for each port.

	Table 11-2. I/O Port Configuration Guide
Port	Where to Find Configuration Information
Ports 1–4	“Bidirectional Port Pin Configurations” on page 7-7 and “Bidirectional Port Considerations”
	on page 7-9
EPORT	“Configuring EPORT Pins” on page 7-17

11-2