Causes for Min FrameErr bit set in CLRC663 for ISO14443 Write

[SasWin]

I use CLRC663 as NFC frontend IC and the NTAG210_NTAG212  (NTAG210 used IC in Murata Tag LXMS33HCNK-171) as target.

I use the CLRC663 without library according to application note AN12657 and use a custom board. 

The detection of the tag works reliable but from time to time (error quote is 5 - 10 %) the CLRC663 cancels my ISO14443 write command due to timeout which is caused by not setting the RxIRQ bit in IRQ0 register. The error register shows me that a Min
FrameErr (error bit 0x10) has occured. What causes this error?

In case that my rf field modulation is not strong enough I would assume a higher error quote of > 50 %. The command itself must be correct, because in most cases It works as expected. 

Are there any additional settings which influence this behaviour?

Kind regards

Sascha

[Fabian_R]

Hello, my name is Fabian, I've been assigned to support your case.

Thank you for your interest in our products

According to the Datasheet (9.6 Contactless interface configuration registers) , this case may appear when a SOF was received correctly but, the frame sent was less than 4 bits.

Is there any chance that this particular Reader may have an issue with the Antenna? Are you able to read any other tag or, to pick up the Antenna's RF Field when the command is sent? You may be able to compare one that works with one that doesn't using a signal analyzer.

[SasWin]

Hi Fabian,

thank you very much for your fast reply.
I can't say for sure, that the reader has no problems with the antenna. My colleague which designed the pcb and the antenna circuit read all relevant application notes, watched the video episodes and follows the general recommendations and hints. Therefore I assume that the hardware is good, maybe not perfect.

Unfortunately I don't have any other tags which uses the ISO14443 protocol. I have 2 tags which uses the ISO15693 protocol and with these tags no problems occured, but the command set, the reader settings and also the requirements concerning the rf field strength and coupling are different. Therefore I don't know whether I can compare these tags.

My current scenario is quite special because I need a test firmware for FCC test. For this test I need a duty cyle of at least one read and write command within one second. At the moment I read and write a tag approximately 6 times per second (without repetitions caused by an error). Could this be to fast? I don't reset the tag to inactive state by turning off the rf field. Due to the high frequency the detection of the erroneous frame is quite hard. I only have an oscilloscope at the moment.

Kind regards

Sascha

[Fabian_R · Accepted solution]

Hello sir,

According to the specification since you are using T2T, the duty cycle should be at 106 kbps. Still this can vary depending on the operation mode and transmission speed.

Since our evaluation  boards have been summited to FCC tests, I'm sure that is achievable on your side either by using our NFC Reader Library or without.

What isn't clear is the amount of failing devices, I don’t think this is due to a SW issue, it may be a HW issue or the environment where those boards are deployed.

[SasWin]

I tested my software again with a tag which I glued directly to my antenna and with a new sensor board with less metal in close area and the error quote dropped dramatically. It seems indeed that the reading range is quite low and even small deviation due to the tag housing or metal from my device lead to some communication problems.

Kind regards

Sascha