IC-MHM Datasheet, PDF (55/63 Pages) IC-Haus GmbH – 14-BIT ABSOLUTE ANGLE HALL ENCODER

iC-MHM
14-BIT ABSOLUTE ANGLE HALL ENCODER
POSITION OFFSET AND PRESET (Zero Position)
Rev D1, Page 55/63
To allow aligning the multiturn absolute position of the
iC-MHM with the connected mechanical system, an
electrical offset is provided. In operation, the offset
value is subtracted from the measured (actual) position
to generate the current position available via the serial
interface in BiSS, SSI, or SPI format. Thus, the position
offset allows defining the zero position of the iC-MHM
to match that of the external mechanical system.
Position Offset
(OFFS_MT and OFFS_ST)
The 48-bit position offset consists of a 32-bit multiturn
and a 16-bit singleturn position offset. These values
are stored in six registers as shown in Table 99.
OFFSET
Address
0x0D
0x0E
0x0F
0x10
0x11
0x12
Addresses 0x0D - 0x12
Name
Description
OFFS_MT
Multiturn Offset Bits 31:24
OFFS_MT
Multiturn Offset Bits 23:16
OFFS_MT
Multiturn Offset Bits 15:8
OFFS_MT
Multiturn Offset Bits 7:0
OFFS_ST
Singleturn Offset Bits 15:8
OFFS_ST
Singleturn Offset Bits 7:0
16-bit singleturn preset position stored in six EEPROM
locations as shown in Table 101.
PRESET
Address
0x48
0x49
0x4A
0x4B
0x4C
0x4D
EEPROM Addresses 0x48 - 0x4D
Name
Description
PSET_MT
Multiturn Preset Position Bits 31:24
PSET_MT
Multiturn Preset Position Bits 23:16
PSET_MT
Multiturn Preset Position Bits 15:8
PSET_MT
Multiturn Preset Position Bits 7:0
PSET_ST
Singleturn Preset Position Bits 15:8
PSET_ST
Singleturn Preset Position Bits 7:0
Table 101: Preset Position
The preset position is protected by its own checksum.
CRC_PSET
Addr. EEPROM 0x4E;
Name
Description
0x00
Checksum for address range 0x48 to 0x4D;
CRC polynomial 0x11D
x⁸ + x⁴ + x³ + x² + 1 (CRC-8)
...
start value 0x02
0xFF
Table 99: Position Offset
Table 102: Preset Position Checksum
The position offset is protected by its own checksum.
CRC_OFFS
Addr. 0x13;
Name
Description
0x00
Checksum for address range 0x0D to 0x12;
CRC polynomial 0x11D
x⁸ + x⁴ + x³ + x² + 1 (CRC-8)
...
start value 0x02
0xFF
Table 100: Position Offset Checksum
The position offset and checksum are calculated by the
iC-MHM during the position preset sequence. In em-
bedded applications using SPI communication without
an external EEPROM, the position offset can also be
calculated by the host processor or microcontroller dur-
ing configuration. Refer to CONFIGURATION on page
52 for more information. The position offset checksum
is not used with SPI mode communication.
Preset Position
In stand-alone systems using BiSS or SSI communi-
cation and an external EEPROM, the 48-bit preset po-
sition defines the location of the zero position of the
iC-MHM relative to the external mechanical system.
The preset position consists of a 32-bit multiturn and a
The preset position must be calculated and stored in the
external EEPROM during iC-MHM configuration. Refer
to CONFIGURATION on page 52 for more information.
Applications without an external EEPROM cannot use
a non-zero preset position.
Position Preset Sequence
A position preset sequence is initiated in response to a
position preset instruction (0x74 = 2), BiSS command 3,
or activation of the dedicated preset input (if configured).
The position preset sequence first performs a CRC on
the preset position value in the external EEPROM. If
the CRC passes or if there is no external EEPROM, the
position preset sequence continues. If the CRC fails,
the iC-MHM is reset.
The iC-MHM next calculates the position offset
(OFFS_MT and OFFS_ST) necessary to make the cur-
rent position (available via the serial interface in BiSS,
SSI, or SPI format) equal to the preset position stored in
the external EEPROM. This new position offset and its
checksum (CRC_OFFS) are then stored in the external
EEPROM for use in subsequent start ups. Finally, the
iC-MHM is reset.
If no external EEPROM is present, the position preset
sequence still proceeds as explained above, but a pre-