Our Advanced Drive Assist Systems(ADAS) project is based on Renesas RH850/U2A16 microcontroller. We are using Infineon Technologies TLE75620-EST, SPI Driver for Enhanced Relay Control IC for driving loads. Datasheet is attached. We don't have any loads connected to SPIDER output pins. We're not commanding digital output logic low or logic high. On power up, SPIDER digital outputs pins are not stable. They are toggling between logic high and logic low. Attached is SPIDER OUT0_HS pin unstable waveform measured with oscilloscope.

When we stop code execution, output pin is stable. Please see attached SPIDER OUT0_HS pin stable waveform.

Microcontroller communicates with SPIDER chip over spi interface. Instead of stopping code execution, if we dynamically disable spi communications, would the digital output become stable?

Why is the digital output toggling? Microcontroller is using spi interface for control and diagnosis. Are we sending something over SPI that's commanding the digital output to toggle?

How do I attach files to this post?

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    \$\begingroup\$ You can insert pictures, links, etc. using the icons at the top of the editor frame when you are creating your question. \$\endgroup\$
    – crj11
    Sep 27, 2020 at 1:29
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    \$\begingroup\$ Who is running around upvoting questions which are desperately short of critically needed details? \$\endgroup\$ Sep 27, 2020 at 4:15
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    \$\begingroup\$ I don't know if this post is serious. Professionals working on Car electronics would not ask such a question - at least not like this. \$\endgroup\$
    – schnedan
    Sep 27, 2020 at 9:15
  • \$\begingroup\$ How are the input pins connected? Accidentally triggering some "limp home" mode via them? \$\endgroup\$
    – Justme
    Sep 27, 2020 at 10:19
  • \$\begingroup\$ For any readers who are interested, the same question was also asked on at least 3 other forums and more information / updates etc. might be supplied there: Electro-Tech-Online.com, All About Circuits and edaboard.com. \$\endgroup\$
    – SamGibson
    Sep 27, 2020 at 21:44

1 Answer 1


Low-level software was writing current to Spider diagnostic open load register periodically for performing open load diagnostics in the off state. This is the reason for toggling behavior at digital ouptput.


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