Datasheet

TMC8462 Datasheet • Document Revision V1.5 • 2019-June-21
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7.11 MFC IO Incremental Encoder Block
This function block provides input pins for incremental encoder signals (two quadrature signals and one
index signal) with differential option. It has a large range of resolution settings, allowing the use of many
different encoders without requiring extra calculations.
Figure 34: MFC IO Incremental Encoder Unit
Encoder Block Configuration Configuration of the Incremental Encoder Block is done via the ENC_MODE
register. Polarities, index event handling, clear and latch options, and prescaler mode can be configured.
N Event Flag The LSB in the ENC_STATUS register shows that an N event has occurred since the last read
access to this register. The flag is cleared on a read access.
Encoder Constant The encoder constant ENC_CONST is added to or subtracted from the encoder
counter on each polarity change of the quadrature signals AB of the incremental encoder. The encoder
constant ENC_CONST represents a signed fixed point number (16.16) to facilitate the generic adaption
between motors and encoders. In decimal mode, the lower 16 bits represent a number between 0 and
9999. For stepper motors equipped with incremental encoders the fixed number representation allows
very comfortable parametrization. Additionally, mechanical gearing can easily be taken into account.
Negating the sign of ENC_CONST allows inversion of the counting direction to match motor and encoder
direction.
The encoder constant can be configured in the ENC_CONST register.
Examples:
• Encoder factor of 1.0:
ENC_CONST = 0x0001.0x0000 = FACTOR.FRACTION
• Encoder factor of -1.0:
ENC_CONST = 0xFFFF.0x0000
This is the two’s complement of 0x00010000. It equals (2
16
-(FACTOR+1)).(2
16
-FRACTION)
• Decimal mode encoder factor 25.6:
ENC_CONST = 00025.6000 = 0x0019.0x1770 = FACTOR.DECIMALS
• Decimal mode encoder factor -25.6:
ENC_CONST = 0xFFE6.4000 = 0xFFE6.0x0FAO.
This equals (2
16
-(FACTOR+1)).(10000-DECIMALS)
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