I/O Ports Overview; Input-Only Port 0 - Intel 8XC196K Series User Manual

I/O ports provide a mechanism to transfer information between the device and the surrounding
system circuitry. They can read system status, monitor system operation, output device status,
configure system options, generate control signals, provide serial communication, and so on.
Their usefulness in an application is limited only by the number of I/O pins available and the
imagination of the engineer.
6.1

I/O PORTS OVERVIEW

Standard I/O port registers are located in the SFR address space and they can be windowed. Mem-
ory-mapped I/O port registers are located in memory-mapped address space. They are indirectly
addressable only, and they cannot be windowed. All ports can provide low-speed input/output
pins or serve alternate functions. Table 6-1 provides an overview of the device I/O ports. The re-
mainder of this chapter describes the ports in more detail and explains how to configure the pins.
The chapters that cover the associated peripherals discuss using the pins for their special func-
tions.
Port Bits
8 (K x )
Port 0
6 (CA, J x )
8 (K x )
Port 1
4 (CA, J x )
8 (K x )
Port 2
6 (CA, J x )
Port 3 8
Port 4 8
Port 5 8
Port 6 8
6.2

INPUT-ONLY PORT 0

Port 0 is an eight-bit, high-impedance, input-only port. Its pins can be read as digital inputs; they
are also inputs to the A/D converter. Port 0 differs from the other ports in that its pins can be used
only as inputs to the digital or analog circuitry.
Table 6-1. Device I/O Ports
Type
Standard Input-only
Standard Bidirectional
Standard Bidirectional
Memory-mapped Bidirectional
Memory-mapped Bidirectional
Memory-mapped Bidirectional
Standard Bidirectional
Direction Associated Peripheral(s)
A/D converter
EPA and timers
SIO, interrupts, bus control, clock gen.
Address/data bus
Address/data bus
Bus control, slave port
EPA, SSIO
CHAPTER 6
I/O PORTS
6-1