IC-MHM Datasheet, PDF (43/63 Pages) IC-Haus GmbH – 14-BIT ABSOLUTE ANGLE HALL ENCODER

iC-MHM
14-BIT ABSOLUTE ANGLE HALL ENCODER
SERIAL INTERFACE: SSI Mode
Rev D1, Page 43/63
The SSI interface is an industry-standard differential se- If MT12 = 0, the multiturn bit length is set by parameter
rial communications interface used for absolute position RESO_MT. Refer to MULTITURN INTERFACE on page
transmission.
23 for more information on RESO_MT.
The serial interface is configured for SSI mode by en-
abling SSI mode (ENSSI = 1) and requires
DISBiSS = 0.
ENSSI
Value
0
1
Address 0x03; bit 7
Serial Mode
BiSS C
SSI
Table 79: BiSS/SSI Protocol Selection
DISBISS
Value
0
1
Addr. 0x07; bit 5
Description
BiSS Enabled
MISO (SLO) Driven High When NCS Inactive
BiSS Disabled
MISO (SLO) in Tristate (High Z) When NCS Inactive
If MT12 = 1, the multiturn bit length still depends on
RESO_MT, but is always fixed at 0, 12, 24, or 32. If the
multiturn resolution (in bits) is less than one of these
values, the multiturn count value is right-justified in the
multiturn field and the unused MSBs are set to zero.
For example, if RESO_MT = 5, the multiturn count is
a 20-bit value in a 24-bit field. In this case, bits 19:0
contain the multiturn count while bits 23:20 are zero.
Refer to MULTITURN INTERFACE on page 23 for more
information on RESO_MT.
The iC-MHM can provide a fixed or adaptive timeout
depending on the setting of parameter NTOA.
Table 80: Disable BiSS Interface
In SSI mode (standard or extended), absolute position
(multiturn count plus singleturn position) may be trans-
mitted in either natural binary or Gray code depending
on parameter BIN_SSI.
NTOA
Value
0
1
Address 0x07; bit 6
Description
Adaptive Timeout (not recommended in SSI mode)
Fixed Timeout
Table 83: Adaptive Timeout
BIN_SSI
Value
0x0
0x1
Address 0x03; bit 5
Numeric Format
Gray Code
Natural Binary
Table 81: SSI Numeric Format
Absolute position values are always transmitted MSB
first regardless of the numeric format.
The bit length of the multiturn count in is set using pa-
rameter MT12.
MT12
Value
0
1
1
1
1
Address 0x03; bit 2
Multiturn Bit Length
As Defined by
RESO_MT
0
12
24
32
Conditions
RESO_MT = 0
RESO_MT = 1, 2, or 3
RESO_MT = 4, 5, or 6
RESO_MT = 7
Table 82: Multiturn Bit Length
If NTOA = 1, a fixed nominal timeout of 20 µs (with a
14 MHz system clock) is used (refer to Elec. Char. item
no. 501 and 904). Use of an adaptive timeout in SSI
mode is not recommended.
The SSI interface can also operate in ring mode by
connecting SLO on the last slave in the SSI chain to
SLI on the first slave. This causes each SSI frame to
be transmitted twice. By checking the repeated position
data for equality, transmission errors can be detected.
After every SSI cycle, the integrity of the configuration
and offset data is verified using a CRC. If either CRC
fails, the appropriate error bit in the error status register
is set, the error output is activated (pin NERR low), and
the extended SSI protocol error bit is activated (nE = 0)
for the next cycle. Refer to STATUS REGISTERS on
page 30 for more information.
In SSI mode, one of two protocols, standard or ex-
tended, may be selected using parameter EXT_SSI.