I'm quite a rookie in the hardware-electronic field so please bear with me. I want to create a multiplexer for JTAG with 1:16, so one input and up to sixteen outputs. Actually I only want to flash the MCU so I don't need specific JTAG possibilities. On this post at TI are some ICs provided which seem to fit but for once I need ICs with more outputs(?) plus I would like to know in general how to choose or rather how to find a suitable IC in general.

In this specific case, the requirements are:

  1. 4 Pin Protocol (5th pin optional) – TCK (Test Clock), TMS (Test Mode Select), TDI (Test Data In), TDO (Test Data Out), TRST (Test Reset – Optional)
  2. Voltage Levels: 1.8V-5V
  3. Frequency: 10MHz-100MHz

Does one need to scroll through endless vendor lists or is there a smarter way to go?

  • 1
    \$\begingroup\$ are you aware that the very idea of JTAG is that you don't need a multiplexer? \$\endgroup\$ Jul 19, 2023 at 12:35
  • 1
    \$\begingroup\$ Is this a multi-up fixture or a single PCBA? Which MCU? What is the maximum length of the boundary scan chain? \$\endgroup\$
    – Lior Bilia
    Jul 19, 2023 at 12:47
  • 1
    \$\begingroup\$ I don't understand what you're trying to achieve here. If you daisy chain your JTAG connections, you can have lots of devices with one JTAG connection (I think there's a limit to the lenght of JTAG chain, but can't remember the details of that). \$\endgroup\$
    – Puffafish
    Jul 19, 2023 at 15:01
  • 1
    \$\begingroup\$ @MarcusMüller I "need" a multiplexer because I don't want to change the software anytime I change something in the chain. \$\endgroup\$
    – Ben
    Jul 20, 2023 at 6:33
  • 1
    \$\begingroup\$ I don't have the datasheets of these two chips at hand, but maybe they are just too slow, or not voltage-tolerant enough, or inferioir to the chips they did present in some other way (power consumption). Or, maybe, they just could not be moved to make a whole-market overview and picked a couple of examples, with sales intent. Again, the principle they demonstrate in the article is what I would go with: write down the requirements of your signal (for JTAG, they even did that for you in the article). Then, go to an electronics distributor website, click to the multiplexers and filter by these. \$\endgroup\$ Jul 20, 2023 at 11:50


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Browse other questions tagged or ask your own question.