Intel 8XC196MC manual Unused Inputs, 13.1.2 I/O Port Pin Connections, I/O Port Configuration Guide

8XC196MC, MD, MH USER’S MANUAL

		Table 13-1. Minimum Required Signals (Continued)
Signal	Type	Description
Name
XTAL1	I	Input Crystal/Resonator or External Clock Input
		Input to the on-chip oscillator and the internal clock generators. The internal clock
		generators provide the peripheral clocks, CPU clock, and CLKOUT signal (MC/MD
		only). When using an external clock or crystal, instead of the on-chip oscillator,
		connect the clock input to XTAL1. The external clock signal must meet the VIH speci-
		fication 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
		an external clock source instead of the on-chip oscillator.

13.1.1 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.

13.1.2 I/O Port Pin Connections

Tie unused input-only port inputs to VSS as shown in Figure 13-1. Chapter 6, “I/O Ports,” contains information about initializing and configuring the ports. Table 13-2 lists the sections, with page numbers, that contain the information for each port.

	Table 13-2. I/O Port Configuration Guide
Port	Where to Find Configuration Information
Port 0	“Standard Input-only Port Considerations” on page 6-4
Port 1	“Standard Input-only Port Considerations” on page 6-4 (MC, MD)
	“Bidirectional Port Pin Configurations” on page 6-9 and “Bidirectional Port Considerations”
	on page 6-12 (MH)
Port 2	“Bidirectional Port Pin Configurations” on page 6-9 and “Bidirectional Port Considerations”
	on page 6-12
Ports 3 and 4	“Bidirectional Ports 3 and 4 (Address/Data Bus) Operation” on page 6-15
Port 5	“Bidirectional Port Pin Configurations” on page 6-9 and “Bidirectional Port Considerations”
	on page 6-12
Port 6	“Configuring Output-only Port Pins” on page 6-17
Port 7 (MD)	“Bidirectional Port Pin Configurations” on page 6-9 and “Bidirectional Port Considerations”
	on page 6-12

13-2