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Microprocessor - Parallel Communication Interface
Reliable, fast and efficient data transfer among different devices is very important in the field of microprocessors and microcontrollers in order to produce optimized performance in the system. There are two key types of data transfer methods in such systems namely, serial communication and parallel communication.
We had a discussion on serial communication and serial communication interface in the previous chapter. This chapter is meant for explaining the concept of parallel communication and Parallel Communication Interface (PCI).
What is Parallel Communication?
In digital systems like microprocessors and microcontrollers, parallel communication is defined as a method for transferring or exchanging multiple bits of digital data or information at the same time.
Parallel communication uses number of conductors equal to the number of data bits to form the communication channel. For example, a 16-bit parallel communication uses 16 parallel conductors and conveys 16-bits simultaneously. Due to transmission of multiple bits at the same time, the parallel communication is much faster than serial communication.
What is Parallel Communication Interface (PCI)?
PCI or Parallel Communication Interface is a communication standard used for faster and efficient data exchange among various electronic devices. PCI allows for transmitting multiple bits of binary data over multiple data lines at the same time. Hence, it enables a faster communication in the microprocessor and microcontroller systems.
In modern microprocessor-based systems, parallel communication interface is used as a bridge between the microprocessor and peripheral or memory devices. It ensures data exchange among different devices with minimal delays and it is widely employed in applications that require high-performance and speed.
Working of Parallel Communication Interface
The working of parallel communication interface can be understood by segmenting it into following three parts, namely −
- Data transmission
- Clock and synchronization
- Addressing and control
In parallel communication interface, data transmission takes place as a transmission of multiple bits simultaneously over multiple communication lines. Where, each communication line conveys one bit of digital data.
The clock signal in parallel communication interface is important for synchronizing data exchange between the sender and receiver. It helps preventing issues like timing mismatches and data corruption.
In addressing and control, the parallel communication interface uses address lines to determine sender and receiver of the data for communication. The control lines are used to manage the flow of data and read/write operations.
Features of Parallel Communication Interface
The following are some key features of the parallel communication interface −
- PCI allows for parallel data transfer i.e., transmission of multiple bits at the same time.
- PCI provides higher data throughput.
- PCI uses a shared clock signal for proper synchronization of all devices.
- PCI provides higher data transfer rates and high bandwidth.
- PCI supports auto-detection feature of connected devices and provides plug-and-play capability.
- PCI can be used for connecting various devices like processors, memory units, IO interfaces, etc.
Types of Parallel Communication Interface
Parallel communication interface has evolved over time to fulfil increasing demands of computing capabilities. The major types of PCI are described below −
- Conventional PCI − This version of PCI was first introduced in the 1990s. It operates at 33 MHz and supports data paths of 32-bits or 64-bits and data transfer rates up to 133 MB/s.
- PCI-X − It is also known as Parallel Communication Interface Extended. This version of PCI was primarily designed for servers and high-performance workstations. It supports higher operating frequencies of up to 133 MHz and bandwidth up to 1 GB/s.
- PCIe − This version is referred to as Parallel Communication Interface Express. This version of PCI makes use of a point-to-point serial communication and provides scalable bandwidth by using lanes x1, x4, x8, and x16. PCI express supports bandwidth up to 32 GB/s and has a backward compatibility with older version of PCI.
Advantages of Parallel Communication Interface
Parallel communication interface offers several advantages, some of which are highlighted below −
- Parallel communication interface provides a faster data transfer rate.
- It reduces delays in data transmission.
- PCI increases system scalability by allowing multiple devices to use a single bus.
- PCI has a wide compatibility as it can be used with microprocessors, graphics units, network cards, IO controllers, etc.
Limitations of Parallel Communication Interface
Despite several advantages, PCI also has certain limitations which are listed below −
- Parallel communication interface is sensitive to noise and signal interference.
- PCI has a limited cable length because data integrity degrades with increasing distance.
- PCI increases complexity and size due to multiple parallel data lines.
Applications of Parallel Communication Interface
Parallel communication interface is used across a wide range of applications, some of which are highlighted here −
- PCI is used in computing systems for connecting peripheral devices like memory module, IO devices, network cards, graphics and sound cards, etc. with microprocessors.
- PCI is also employed in embedded systems for enabling high-speed data exchange between processors and memory devices.
- In network devices like switches, routers, and network interface cards are used for providing fast data transfer.
- Industrial automation and control systems also use parallel communication interface for enabling real-time communication between sensors and controllers.
Conclusion
Parallel Communication Interface (PCI) is an important technology in modern computing and embedded systems. It is known for providing high-speed data transfer between digital devices and improving system performance. In this chapter, we provided a comprehensive overview of parallel communication and parallel communication interface.