topic Re: The rdtx output of mc33664 is abnormal in S32K

The rdtx output of mc33664 is abnormal

zuozuo — Tue, 24 Mar 2026 10:32:12 GMT

Currently, I am using s32k344 to control MC33664. The en pin is at a high level, and the intb pin is pulled low from high and then quickly pulled high. The SPI control pin of s32k344 has SCK with the correct waveform and data pin. However, when using an oscilloscope to collect RDTX+and RDTX - of MC33664, the waveforms are shown in the attached image, and the trends of the two waveforms are consistent. Why?

Re: The rdtx output of mc33664 is abnormal

TomasVaverka — Tue, 24 Mar 2026 12:32:22 GMT

Hi,

Please take a close look at our AN12605, especially at the Master Node Typical Schematic (Figure 5 and Figure 7) to verify the following:

Termination: Ensure the mandatory external resistor (or split filter) is correctly placed between the corresponding pins.

Transformer Isolation: Check for a short circuit between the transformer primary and secondary traces.

Power Supply: Confirm VCC is at the specified level. While the IC operates down to its minimum voltage, the recommended VCC is required to achieve the specified output levels.

BRs, Tomas

Re: The rdtx output of mc33664 is abnormal

zuozuo — Wed, 25 Mar 2026 00:18:31 GMT

The stable AN12605 you shared cannot be opened by me, and I couldn't find it even after searching. Can you share a link that is easier to open?

Re: The rdtx output of mc33664 is abnormal

TomasVaverka — Wed, 25 Mar 2026 08:41:09 GMT

Hi,

The AN12605 is classified as a Secure file requiring the NDA.

If your company has not signed the NDA with NXP yet, you can request it from:
https://www.nxp.com/support/support:SUPPORTHOME

If there is a valid NDA in place, you can download the AN12605 from the following website:
https://www.nxp.com/products/MC33664

Kindly check FAQs to understand the process:
https://www.nxp.com/support/support/secure-access-rights:SEC-ACCESS

https://www.nxp.com/support/support/secure-access-rights/secure-access-rights-faqs:SEC-ACCESS-FAQS

BRs, Tomas

Re: The rdtx output of mc33664 is abnormal

zuozuo — Fri, 27 Mar 2026 05:57:10 GMT

https://community.nxp.com/t5/S32K-Knowledge-Base/S32K344-MC33664-MC33775-RTD-3-0-0-BMS-SDK-1-0-2/ta-p/2127049

Hello, tomasvaverka, Now, I can capture the correct waveform. Using the program provided by the link and based on the modified reference program of our test bench, the first main modification is to modify the SPI pin, and the other is to shield the code of the red line shown in the picture (Figure 1). The main modification is to cancel the MC33775_CDD_SCC_SWC_Snit_Slot2 function in the CDD_BC_SWC_SlotInit function, so that it is powered on and MC33775_CDD_SCC_SWC_Snit_Slot3 is generated. The initialization generates a wake-up signal. However, I captured the SPI signal through an oscilloscope and obtained its value as shown in Figure 2. As I know from the MC33775 data manual, when I set one daisy chain, one MC33775 In the case of 75, the wake-up signal data field value is 0xffee, and now all the signals I have collected are 0. Please help me!