1- What is a termination resistor
2- Why is it needed in RS422/RS485
3- When and where to use a termination resistor
In this blog, we will explain briefly when termination resistors are needed in RS-422/RS-485 along with their applications and implementations on DSBOARD-NX2.
For RS-422/RS-485, applications requiring long distance cables and high data rates, so placing a termination resistor between differential lines is crucial to maintain a healthy communication.
In half-duplex configuration (RS-485 2-wire), termination resistors must only be placed on the devices at both ends, not on the ones in between.
Figure 3 from Analog Devices Application Note AN-960: Half-Duplex Configuration
In full-duplex configuration (RS-422 or RS-485 4-wire), there must be termination resistors on receiver sides of both master device and the furthest slave device.
Figure 4 from Analog Devices Application Note AN-960: Full-Duplex Configuration
If you’re planning to use DSBOARD-NX2 at one end as mentioned above, there is an option to place the termination resistors on-board. You can place a 0402 sized 120Ω (or other desired value) resistor in place of R1608 for half-duplex applications or R1609 for full-duplex applications.
Also, by reducing bus speed, you may improve long distance performance substantially or avoid the usage of termination resistors. This option is also available on DSBOARD-NX2. In cases where you don’t need the default 20Mbps data rate, you may limit it to 250kbps by removing R1607 and placing a 0402 sized 0Ω in place of R1611.
Thank you for reading our blog post.
If you want to get updated on new blog posts, product launches and discounts, you can fill out the form and sign up for our newsletter. By signing up, you can reach various blog posts about AI, deep learning, machine vision, high-speed cameras, and industrial interfaces.
You will receive a "free shipping" code for next purchase immediately.