82C54
82C54 Programmable Interval Timer
Overview
The 82C54 is a high-performance, programmable interval timer/counter designed for use in microprocessor-based systems. This component provides three independent 16-bit counters, each capable of handling clock inputs up to 8 MHz. The 82C54 is fabricated using CMOS technology, offering low power consumption while maintaining compatibility with the industry-standard 8254 timer.
This versatile timer IC is particularly useful in applications requiring precise timing, event counting, or waveform generation. Its programmable nature allows system designers to configure each counter independently for different timing operations, making it suitable for complex timing requirements in computer systems, industrial control, and instrumentation applications.
Features
- Three independent 16-bit counters
- Programmable count modes (6 different modes)
- Counts in binary or BCD
- Maximum clock frequency: 8 MHz
- Low power CMOS technology
- Single +5V power supply
- Fully compatible with 8254 timer
- 24-pin DIP and PLCC package options
- Bidirectional tri-state data bus interface
- Status read-back command
Applications
The 82C54 finds application in numerous systems requiring precise timing and counting functions:
- Real-time clock generation
- Digital frequency synthesis
- Event counting in industrial systems
- Motor speed control and measurement
- Waveform generation
- Computer system timing (DRAM refresh, speaker tones)
- Process control systems
- Communication systems (baud rate generation)
- Test and measurement equipment
Electrical Characteristics
Absolute Maximum Ratings
- Supply Voltage (Vcc): -0.5V to +7V
- Input Voltage: -0.5V to Vcc +0.5V
- Operating Temperature Range: 0°C to +70°C (Commercial)
- Storage Temperature Range: -65°C to +150°C
Recommended Operating Conditions
- Supply Voltage (Vcc): +4.5V to +5.5V
- Input High Voltage (VIH): 2.0V min
- Input Low Voltage (VIL): 0.8V max
- Output High Voltage (VOH): 2.4V min (Ioh = -2.5mA)
- Output Low Voltage (VOL): 0.45V max (Iol = 2.5mA)
- Clock Frequency: 0 to 8 MHz
DC Characteristics
- Power Supply Current (ICC): 10mA max (at 5V, 8MHz)
- Input Leakage Current (IIL): ±10μA max
- Output Leakage Current (IOZ): ±10μA max
- Input Capacitance (CIN): 10pF max
AC Characteristics
- Clock Pulse Width (tCLK): 125ns min
- Read Pulse Width (tRD): 300ns min
- Write Pulse Width (tWR): 300ns min
- Chip Select Setup Time (tCSS): 100ns min
- Data Setup Time (tDS): 100ns min
- Data Hold Time (tDH): 30ns min
Functional Description
The 82C54 consists of three identical 16-bit counters that can operate independently. Each counter has a clock input (CLK), gate input (GATE), and output (OUT). The counters are programmed by writing control words to the control word register, which determines the operating mode, count format (binary or BCD), and loading sequence.
Counter Modes
- Mode 0: Interrupt on Terminal Count
- Mode 1: Hardware Retriggerable One-Shot
- Mode 2: Rate Generator
- Mode 3: Square Wave Generator
- Mode 4: Software Triggered Strobe
- Mode 5: Hardware Triggered Strobe
Programming the 82C54
To program the 82C54, the microprocessor must write a control word followed by the initial count value. The control word specifies which counter is being programmed, the operating mode, count format (binary or BCD), and the loading order (LSB only, MSB only, or LSB then MSB).
Package Information
24-Pin DIP Package
- Package Type: PDIP-24
- Dimensions: 31.75mm x 6.35mm
- Pin Spacing: 2.54mm
- Row Spacing: 15.24mm
- Material: Plastic
24-Pin PLCC Package
- Package Type: PLCC-24
- Dimensions: 8.89mm x 8.89mm
- Lead Pitch: 1.27mm
- JEDEC Standard: MO-047
- Material: Plastic
Pin Configuration
24-Pin DIP Pinout
- Pin 1-8: D7-D0 (Data Bus)
- Pin 9: GND (Ground)
- Pin 10: CLK2 (Counter 2 Clock Input)
- Pin 11: OUT2 (Counter 2 Output)
- Pin 12: GATE2 (Counter 2 Gate Input)
- Pin 13: GATE1 (Counter 1 Gate Input)
- Pin 14: CLK1 (Counter 1 Clock Input)
- Pin 15: OUT1 (Counter 1 Output)
- Pin 16: Vcc (+5V Power Supply)
- Pin 17: RD (Read Input)
- Pin 18: WR (Write Input)
- Pin 19: CS (Chip Select)
- Pin 20: A1 (Address Line 1)
- Pin 21: A0 (Address Line 0)
- Pin 22: GATE0 (Counter 0 Gate Input)
- Pin 23: CLK0 (Counter 0 Clock Input)
- Pin 24: OUT0 (Counter 0 Output)
Conclusion
The 82C54 Programmable Interval Timer offers a flexible and reliable solution for timing and counting applications in microprocessor-based systems. With its three independent counters, multiple operating modes, and CMOS low-power design, it provides system designers with a versatile timing component suitable for a wide range of applications. The device's compatibility with the industry-standard 8254 timer ensures easy integration into existing designs while offering improved performance and power characteristics.
