Technical Summary for 82C55 Programmable Peripheral Interface

82C55 Programmable Peripheral Interface (PPI)

Overview

The 82C55 is a high-performance, CMOS version of the industry-standard 8255A Programmable Peripheral Interface (PPI) chip. It is designed to provide flexible I/O capabilities for microprocessor-based systems. The 82C55 features three 8-bit ports (Port A, Port B, and Port C) that can be independently programmed to operate in various modes, making it suitable for a wide range of interfacing applications. Its CMOS technology ensures low power consumption while maintaining compatibility with TTL levels.

Key Features

Three 8-bit I/O Ports: Port A, Port B, and Port C provide 24 programmable I/O pins.
Multiple Operating Modes: Supports Mode 0 (Basic Input/Output), Mode 1 (Strobed Input/Output), and Mode 2 (Bidirectional Bus).
Bit Set/Reset Capability: Individual bits of Port C can be set or reset for control applications.
CMOS Technology: Low power consumption and high noise immunity.
TTL Compatibility: All inputs and outputs are TTL-compatible.
Flexible Interface: Can interface with most 8-bit and 16-bit microprocessors.
Wide Operating Voltage: Typically operates at 5V ±10%.

Applications

The 82C55 is widely used in various embedded and industrial applications, including:

Microprocessor/Microcontroller Interfacing: Acts as a bridge between the CPU and peripheral devices.
Data Acquisition Systems: Used for reading sensors and controlling actuators.
Industrial Control Systems: Provides programmable I/O for machinery and automation.
Keyboard and Display Interfaces: Facilitates communication with input/output devices.
Communication Systems: Used in parallel data transfer applications.
Test and Measurement Equipment: Enables flexible signal routing and control.

Electrical Characteristics

Absolute Maximum Ratings

Supply Voltage (V_CC): -0.5V to +7V
Input Voltage (V_IN): -0.5V to V_CC + 0.5V
Operating Temperature Range: -40°C to +85°C
Storage Temperature Range: -65°C to +150°C

DC Characteristics (V_CC = 5V ±10%, T_A = 25°C)

High-Level Input Voltage (V_IH): Min. 2.0V
Low-Level Input Voltage (V_IL): Max. 0.8V
High-Level Output Voltage (V_OH): Min. 2.4V @ I_OH = -2.5mA
Low-Level Output Voltage (V_OL): Max. 0.4V @ I_OL = 2.5mA
Supply Current (I_CC): Max. 10mA (active mode)

AC Characteristics

Read Cycle Time (t_RC): 300ns (max)
Write Cycle Time (t_WC): 300ns (max)
Address Setup Time (t_AS): 100ns (min)
Data Hold Time (t_DH): 50ns (min)

Package Information

The 82C55 is available in two common package types:

40-Pin Dual Inline Package (DIP):
- Package Dimensions: 52.32mm x 13.97mm
- Pin Spacing: 2.54mm (0.1")
- Material: Plastic
44-Pin Plastic Leaded Chip Carrier (PLCC):
- Package Dimensions: 16.51mm x 16.51mm
- Lead Pitch: 1.27mm (0.05")
- Material: Plastic

Pin Configuration (DIP and PLCC)

The following table summarizes the pin functions for both package types:

PA0-PA7 (Pins 1-8 / 2-9): Port A I/O pins (8-bit)
PB0-PB7 (Pins 9-16 / 10-17): Port B I/O pins (8-bit)
PC0-PC7 (Pins 17-24 / 18-25): Port C I/O pins (8-bit)
CS (Pin 25 / 26): Chip Select (active low)
RD (Pin 26 / 27): Read Control (active low)
WR (Pin 27 / 28): Write Control (active low)
A0-A1 (Pins 28-29 / 29-30): Address Lines for port selection
RESET (Pin 30 / 31): Reset Input (active high)
V_CC (Pin 40 / 44): +5V Power Supply
GND (Pin 20 / 21): Ground

Functional Description

The 82C55 operates by programming its control register to define the behavior of its three ports. The control word format allows selection of operating modes for each port group (Group A: Port A and upper Port C; Group B: Port B and lower Port C). Key functional aspects include:

Mode 0 (Basic I/O): All ports function as simple input or output ports with no handshaking.
Mode 1 (Strobed I/O): Ports A and B use Port C lines for handshaking and interrupt generation.
Mode 2 (Bidirectional Bus): Port A becomes bidirectional with handshaking signals from Port C.
Bit Set/Reset Mode: Allows individual bits of Port C to be set or reset without affecting other bits.

Programming Considerations

To use the 82C55, the system software must:

Initialize the control register with the desired operating mode configuration
Access the ports according to the selected mode
Handle interrupts if Mode 1 or Mode 2 is used (requires proper interrupt service routine)

The control word format is as follows:

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