In the context of microcontrollers, PSP stands for Parallel Slave Port. It is a specific type of interface found on some microcontrollers, particularly certain models of PIC microcontrollers.
Understanding the Parallel Slave Port (PSP)
The Parallel Slave Port is designed to facilitate communication between a microcontroller and other external devices. Unlike serial interfaces (like UART or SPI) that send data one bit at a time, a parallel port transfers multiple bits simultaneously. The "Slave" designation means the port typically waits for a "master" device (like another microcontroller or a computer) to initiate and control the data transfer process.
Based on the provided reference:
- A parallel slave port (PSP) is an interface found on some PIC microcontrollers.
- It allows 8-bit asynchronous bidirectional data transfer.
- It is used for communication between the PIC microcontroller and external devices, such as other microcontrollers or personal computers.
This means the PSP can send and receive 8 bits of data at the same time, making it potentially faster for bulk data transfer compared to 1-bit serial methods, especially when operating asynchronously (without a shared clock signal between devices, relying on handshake signals instead).
Key Features of the PSP
- 8-Bit Data Width: Transfers a full byte (8 bits) concurrently.
- Bidirectional: Can send data out or receive data in.
- Asynchronous: Data transfer doesn't require a shared clock signal between the master and slave; instead, it uses handshake signals (like
RD,WR,CS,INT) to manage the flow. - Slave Operation: Designed to respond to commands or requests from a master device.
- External Communication: Primarily used to interface the microcontroller with other chips or systems.
How the PSP Works
The PSP typically uses a set of data pins (usually 8, for the 8 bits) and several control pins. The control pins are essential for managing the asynchronous data transfer. Common control signals include:
- Chip Select (CS): Activates or deactivates the PSP for communication.
- Read (RD): Signal from the master indicating it wants to read data from the PSP.
- Write (WR): Signal from the master indicating it wants to write data to the PSP.
- Interrupt (INT): Signal from the PSP to the master, often used to indicate that data is ready or an event has occurred.
When the master device wants to communicate, it asserts the appropriate control signals (like CS, RD, or WR) and places data on or reads data from the data pins. The slave (the PIC microcontroller with the PSP) monitors these signals and responds accordingly, facilitating the handshake and data transfer.
Applications of PSP
The PSP is useful in scenarios where an 8-bit parallel data path is advantageous for communication with external components or systems. Examples include:
- Interfacing with other microcontrollers: Allows two microcontrollers to exchange data efficiently.
- Connecting to external memory: Though less common now, historically parallel ports were used for certain types of memory interfaces.
- Communicating with PCs or other host systems: Enables a microcontroller to act as a peripheral device that a computer can quickly read data from or write data to.
The PSP offers a direct, byte-wide data path, providing a balance between the simplicity of serial communication and the speed of synchronous parallel interfaces like dedicated memory buses. Its implementation details can vary slightly between different PIC microcontroller families.
