Universal Verification Methodology Based Verification of UART Protocol

Abstract

Verification today acts as a constriction of any complex VLSI design. Bringing out improved verification efficiency is a must. Most of the computers and microcontrollers contain a number of serial data ports. These data ports are used to connect with devices such as keyboards and printers which are basically serial input and output devices. Transmission and reception of serial data from an isolated location can be done with the help of a modem connected to the serial port. UART- Universal Asynchronous Receiver and transmitter is a hardware device which facilitates serial transmission and reception of data. In this work presented here, the UART has been designed with the use of the industry standard Verilog HDL code and the verification of the protocol has been done using system Verilog code in UVM environment. The UVM based verification methodology can significantly reduce the time needed for verification.

Design And Implementation of UART Based on Verilog HDL

“…The starting bit is sent first, followed by 8 valid data bits, the low bit is sent first, the high bit is sent last, and bits 1-7 of the byte are sent successively [5].…”

“…The sender rs232_tx sends serial data in r_data according to the count of bit_cnt. When bit_cnt counts to 10 and bit_flag is high level, a done signal is generated, making the state set to low level to end the transmission [9] 4'd4:rs232_tx <= r_data [3]; 4'd5:rs232_tx <= r_data [4]; 4'd6:rs232_tx <= r_data [5]; 4'd7:rs232_tx <= r_data [6]; 4'd8:rs232_tx <= r_data [7]; 4'd9:rs232_tx <= 1'b1; default:rs232_tx <= 1'b1; endcase end end else rs232_tx <= 1'b1; end When the send flag bit_flag is high, the bit counter bit_cnt starts countingWhen bit_cnt is 0, rs232_tx sends out starting bit (low level). When bit_cnt ranges from 1 to 8, rs232_tx sends eight bits of r_data from low to high.…”

UART communication protocol frame format explanation and application

“…From equation (2), it can be seen that the bit rate and baud rate are equal for asynchronous serial communication using NRZ coding method [8]. Therefore, by measuring the minimum bit-width time of data in asynchronous serial communication, the bit rate of asynchronous serial communication can be deduced as equivalent to the baud rate of asynchronous serial communication obtained.…”

“…Each data bit has a clock error, and the receiver can also accurately sample data bits, greatly improving the reliability and anti-interference ability of asynchronous communication. During the sampling process of received data, the sampling point is located in the middle of each data bit, and data sampling is conducted every 16 sampling clocks [8]. This sampling method can effectively avoid edge distortion at both ends of the data bit, and avoid errors caused by incomplete synchronization of asynchronous clocks between the transmitter and receiver.…”

“…Alternatively, establishing a framing protocol assures security because the information received must be parsed in accordance with the framing protocol's architecture. Each frame protocol is specifically created to guarantee safety and uniqueness [8].…”