MLX90132 Datasheet, PDF (34/44 Pages) Melexis Microelectronic Systems – 13.56MHz RFID / NFC Transceiver

MLX90132
13.56MHz RFID / NFC Transceiver
10 Electromagnetic support (EMD)
The electromagnetic disturbance results in the noise that a passive/active TAG or NFC device generates
before answering to a corresponding request. This disturbance is generally due to the digital processing of
the passive/active TAG or NFC device which appears just before sending back the response.
The MLX90132 device supports a specific algorithm to filter EMD disturbances to successfully receive the
frame from a passive/active TAG or NFC device. This algorithm is supported within the MLX90132 in Reader
modes ISO14443 type-A and type-B.
The following flow-charts illustrate the algorithm which is implemented in the MLX90132 device for these 2
modes of operation. The corresponding EMD algorithm is selected with the Protocol select command (0x02)
by configuring the parameter <N_EMD> with a non-null value. The definition of the two values <N_EMD> and
<N_EMD,RES> used in the algorithm are defined below:
 <N_EMD>: Maximum Number of non-valid Bytes received, before the system leaves the EMD algorithm
routines with an error message. Typically, this value is set to 3 or 4, meaning that failing reception with
less than 3 or 4 Bytes will be considered as EMD disturbance by the algorithm without interrupting the
reception process.
 <N_EMD,RES>: Maximum Number of non-valid and non-Integer Bytes received, before the system leaves
the EMD algorithm routines with an error message. Typically, this value is set identical to the N_EMD value.
When processing the EMD algorithm, the MLX90132 is in kind of “standalone” mode, waiting for the presence
of a valid <Start Of Frame> coming for the passive/active TAG or NFC device. This “standalone” mode only
terminates with the following conditions:
1) At the end of a valid reception
2) In case a timeout error occurs (FDT/FWT time reached without valid SOF)
3) In case the identified error could be assimilated as a protocol error and not to EMD
During the whole EMD process, the MLX90132 is buffering the incoming errors which will be returned to the
host application in case one of the conditions 2) or 3) above is reached. In this case, the error code returned
will be as follows:
<ErrorCode> + <ErrorBufLen> + <ErrorBuf> with
 <ErrorCode>: Last error code raised during the EMD algorithm
 <ErrorBufLen>: Length of the following Buffer of Errors (max. 8 bytes)
 <ErrorBuf>: Buffer of Errors stored during the EMD algorithm (max. 8 bytes)
3901090132
Rev. 009
Page 34 of 44
Jan-2014