KMA199 datasheet(21/36 Pages) NXP

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KMA199_1

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Product data sheet

Rev. 01 — 26 April 2010

21 of 36

NXP Semiconductors

KMA199

Programmable angle sensor

13.3.3 Entering the command mode

After a power-on reset, the sensor provides a time slot tcmd(ent) for entering the command

mode. A specific command sequence has to be send (see Figure 17). If command mode

is not entered, the sensor starts in the normal operating mode. However the signature can

be written by the master, if the sensor switches to diagnostic mode.

During the command mode sequence, the analog output is enabled. The external

programming hardware has to overdrive the output with the current Iod. If command mode

is activated, the analog output is disabled and pin OUT/DATA operates as a digital

interface.

13.4 Cyclic redundancy check

As already mentioned in Section 7, there is an 8-bit checksum for the EEPROM data.

To calculate this value, the CRC needs to be generated with the MSB of the EEPROM

data word at first over all corresponding addresses in increasing order.

All addresses from 0h to Fh have to be read out for calculating the checksum. The Least

Significant Byte (LSB) of address Fh which contains the previous checksum must be

overwritten with 0h before the calculation can be started.

Finally, the internal charge pump has to be enabled for programming by setting the bits

EEP_CP_CLOCK_EN and EEP_WRITE_EN (see Table 16) and waiting for tcp.

The generator polynomial for the calculation of the checksum is:

(9)

With a start value of FFh and the data bits are XOR at the x8 point.

Fig 17. OWI command mode procedure

001aag819

tcmd(ent)

signature

command

START

OWI

VDD

94h

9Bh

A4h

STOP

()

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