IC-MHM Datasheet, PDF(53/63 Page) IC-Haus GmbH – 14-BIT ABSOLUTE ANGLE HALL ENCODER

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IC-MHM Datasheet, PDF (53/63 Pages) IC-Haus GmbH – 14-BIT ABSOLUTE ANGLE HALL ENCODER

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iC-MHM

14-BIT ABSOLUTE ANGLE HALL ENCODER

Rev D1, Page 53/63

setting the chip as explained above, ERR_CFG = 1,

ERR_OFFS = 1, the error output is still active (pin

NERR low), and the error bit in the BiSS SCD, SPI

position read command response, and extended SSI

frame are still active (nERROR = nE = 0) since the CRC

tests fail because the configuration and offset check-

sums (CRC_CFG and CRC_OFFS, respectively) have

not been configured. However, SLO is released and the

remainder of the configuration parameters can be writ-

ten using full bidirectional BiSS communication while

ignoring the errors.

Once all the configuration parameter values have

been written, the configuration and offset checksums

(CRC_CFG and CRC_OFFS, respectively) must be cal-

culated and stored in RAM. Please use therefore CR-

C-Polynomial = 100011101 and start value = 2. A sam-

ple C++ CRC checksum calculation routine is shown

following.

Example of CRC Calculation Routine

With the checksums stored, the iC-MHM has to be reset

by writing Address (0x74 = 1).

If an EEPROM is connected to the iC-MHM (refer

to EEPROM AND I2C INTERFACE on page 33), the

complete configuration (including checksums) must

be written to it for use on subsequent start ups.

Write the configuration data in RAM addresses 0x00

- 0x13 to EEPROM addresses 0x10 - 0x23 byte by

byte using BiSS register write commands. Refer to

the BiSS Interface Protocol Description (C-Mode) at

www.biss-interface.com for more information on BiSS

If a position preset command or enabled preset input

P1 is required by the application, a value for the preset

position and its checksum must also be written to the

EEPROM as part of iC-MHM configuration. Write the

desired preset position and its checksum to EEPROM

addresses 0x48 - 0x4E byte by byte using BiSS reg-

ister write commands. Refer to POSITION OFFSET

AND PRESET (Zero Position) on page 55 for more

information.

unsigned char Reg[20] = {0x44, 0x47, 0x10, 0x1A,

0x80, 0x00, 0x10, 0x00, 0x03, 0x80, 0x00,

0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,

0x00, 0x00};

int iCRCPoly = 0x11D; // CRC-Polynomial 100011101

unsigned char ucDataStream = 0;

unsigned char ucCRC;

// Calculate Config-CRC //

ucCRC = 2; // startvalue !!!

for (int iReg = 0 ; iReg<12; iReg ++) {

ucDataStream = Reg[iReg];

for (int i =0; i <=7; i ++) {

if ( (ucCRC & 0x80) != (ucDataStream & 0x80))

ucCRC = (ucCRC << 1 ) ^ iCRCPoly ;

else

ucCRC = (ucCRC << 1 ) ;

ucDataStream = ucDataStream << 1 ;

}

Reg[12] = ucCRC;

When writing to the EEPROM, a wait time of at least

4 ms must be allowed after each write. Alternatively, the

same byte can be read back after it is written and the

values compared. This comparison will fail if the EEP-

ROM is busy with its internal write procedure. Several

attempts may be required for the read value to equal

the written value before the next location can be written.

SPI Mode Configuration

In SPI mode, use Register Write (Continuous) com-

mand to write all configuration parameters and then

reset the iC-MHM. Refer to SERIAL INTERFACE: SPI

Mode on page 46 for more information.

// Calculate Offset-CRC //