Intel 8XC196NT, User Manual

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8XC196NT USER’S MANUAL
12-2
12.1.1 Unused Inputs
For predictable performance, it is important to tie unused inputs to V
CC
or V
SS
. Otherwise, they
can float to a mid-voltage level and draw excessive current. Unused interrupt inputs may generate
spurious interrupts if left unconnected.
12.1.2 I/O Port Pin Connections
Tie unused input-only port inputs to V
SS
as shown in Figure 12-1. Chapter 6, “I/O Ports,” contains
information about initializing and configuring the ports. Table 12-2 lists the sections, with page
numbers, that contain the information for each port.
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. 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 V
IH
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.
Table 12-2. I/O Port Configuration Guide
Port Where to Find Configuration Information
Port 0 “Standard Input-only Port Considerations” on page 6-3
Ports 1 and 2 “Bidirectional Port Pin Configurations” on page 6-9 and “Bidirectional Port Considerations”
on page 6-11
Ports 3 and 4 “Bidirectional Ports 3 and 4 (Address/Data Bus) Operation” on page 6-15
Ports 5 and 6 “Bidirectional Port Pin Configurations” on page 6-9 and “Bidirectional Port Considerations”
on page 6-11
EPORT “Configuring EPORT Pins” on page 6-24
Table 12-1. Minimum Required Signals(Continued)
Signal
Name
Type Description