Serial Link Peripheral Documentation

Overview

The Serial Link peripheral (GitHub Repository) is integrated into X-HEEP. It provides a mechanism to transmit data through a serial interface using a FIFO buffer of configurable size.

Unlike direct memory access, the serial link does not write output directly to memory or a specific address. Instead, data is first stored in a FIFO, which can be accessed as a memory-mapped peripheral. This allows software and hardware to interact with the transmitted data efficiently.

Features

• Memory-mapped peripheral: The serial link itself is memory-mapped, enabling software access to transmitted data through a standard interface.

• FIFO buffering: All transmitted data is stored in a FIFO of configurable depth before being sent.

• Configurable payload: The data to be transmitted, referred to as the payload, is declared in the ip/serial_link/minimal_pkg.sv package.

  • This ensures that the vendored serial link files remain untouched.

  • Other configurable parameters are also declared in the same package.

Configuration

1. FIFO Size: The depth of the FIFO can be adjusted according to system requirements.

2. Payload Definition:

   • Located in ip/serial_link/minimal_pkg.sv.

   • Contains the data to be transmitted and other configuration parameters.

3. Register Programming:

   • To use the serial link, the memory-mapped registers must be correctly programmed.

   • The initialization function sl_init provides the required register setup.

4. Integration:

   • The peripheral is memory-mapped in X-HEEP.

   • Only the FIFO is written by the peripheral; memory writes occur through standard memory-mapped access.

Software Application

• A test harness simulation is included to demonstrate the current functionality of the serial link.

• The software interacts with the FIFO to read transmitted data and verify correct operation.

• Use sl_init to initialize the peripheral and program all required registers before transmitting data.

Usage

1. Call sl_init to program the serial link registers.

2. Write data to the serial link peripheral.

3. The data is stored in the FIFO.

4. Read data from the FIFO through the memory-mapped interface.

5. The data is transmitted over the serial interface according to the payload configuration.

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Note: This documentation describes the minimal configuration and usage of the Serial Link peripheral within X-HEEP. For advanced features and customizations, refer to the original vendor documentation.

Note: If you are using verilator 4.210, make sure to disable the Serial Link (not include it) because it is not capable of compiling it. Use verilator 5.040 instead.