FPGA (Field Programmable Gate Array) is a highly flexible integrated circuit that can be programmed to implement a variety of digital functions. Implementing a single bus protocol in FPGA can effectively simplify communication between modules. A single bus protocol refers to a communication line (bus) shared by all devices or modules, which can reduce the complexity and cost of hardware connections.

1.What is a single bus protocol?

The single bus protocol is a shared bus communication method, the main feature of which is that all devices share a communication line. Usually, a single bus system includes a master module (Master) and one or more slave modules (Slave). The master module is responsible for initializing communication and controlling data transmission, while the slave module responds to the master module's request after receiving instructions.

2.Common single-bus protocols

In FPGA design, common single-bus protocols include I2C (Inter-Integrated Circuit), SPI (Serial Peripheral Interface), and 1-Wire protocols. Each protocol has its specific application scenarios and advantages and disadvantages.

①I2C (Inter-Integrated Circuit)

I2C is a two-wire serial communication protocol invented by Philips. The I2C protocol uses two lines for communication: a data line (SDA) and a clock line (SCL).


  • Simple two-wire design reduces hardware connections.
  • Supports multiple masters and multiple slaves.
  • Widely used in sensors and low-speed peripherals.

Implementation: The I2C protocol is usually implemented in FPGA through Verilog or VHDL, including a master module and a slave module. The master module is responsible for generating a clock signal and controlling data transmission, and the slave module receives and sends data synchronously according to the clock signal of the master module.

②SPI (Serial Peripheral Interface)

SPI is a synchronous serial communication protocol, usually used for high-speed data transmission. SPI uses four lines: data input (MISO), data output (MOSI), clock (SCLK), and slave select (SS).


  • High-speed data transmission.
  • Full-duplex communication (simultaneous data transmission and reception).
  • Simple hardware implementation.

Implementation: To implement the SPI protocol in FPGA, you need to design a master module and a slave module. The master module generates a clock signal and controls the slave select line. The slave module synchronizes data transmission based on the select line and clock signal.

③1-Wire protocol

The 1-Wire protocol was developed by Dallas Semiconductor (now Maxim Integrated) and is a single-wire communication protocol mainly used for low-speed devices.


  • Only one data line is required, saving hardware resources.


  • Simple bus structure, suitable for simple sensors and identification devices.

Implementation: To implement the 1-Wire protocol in FPGA, you need to design a master module to perform all communications through a single data line. The implementation of the protocol involves bus multiplexing, timing control, and the sending and receiving of data frames.

3.Design and implementation

Implementing a single bus protocol in an FPGA usually includes the following steps:

①Define interface signals

Define interface signals related to the protocol, such as SDA and SCL signals of I2C, MISO, MOSI, SCLK and SS signals of SPI, and single-wire signals of 1-Wire.

②Write HDL code

Use Verilog or VHDL to write the code for the master and slave modules. The timing, data frame format and state machine of the protocol need to be described in detail.

③Bus arbitration and conflict detection

If the protocol supports multiple masters, bus arbitration and conflict detection mechanisms need to be implemented. For example, the I2C protocol implements arbitration for multiple masters by detecting the idle state of the bus.

④Testing and verification

Verify the correctness of the design through simulation tools and actual hardware testing. Functional testing, timing analysis and performance evaluation are required to ensure that the protocol works as expected.

4.Sample code

The following is a Verilog code example for a simple I2C master module: