ST7FMC1K2B3 STMICROELECTRONICS [STMicroelectronics], ST7FMC1K2B3 Datasheet - Page 180

• Manufacturer Part Number: ST7FMC1K2B3
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

ST7MC1xx/ST7MC2xx
MOTOR CONTROLLER (Cont’d)
10.6.7.5 Speed Measurement Mode
Motor speed can be measured using two methods
depending on sensor type: period measurement or
pulse counting. Typical sensor handling is de-
scribed here.
Incremental encoders allows accurate speed
measurement by providing a large number of puls-
es per revolution (ppr) with ppr rates up to several
thousands; the higher the ppr rate, the higher the
resolution. The proposed method consists of
Figure 99. Tachogenerator period acquisition using MTIM timer
Figure 100. Encoder Clock frequency measure using MTIM timer
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1
(triggered by software
C
C
or Real-time Clock)
MTIM Counter
Comparator
Capture
MTIM Counter
Interrupts
Compare
Capture
Output
Tacho
Value
Value
Interrupts
Encoder
Value
Clock
To interrupt generator
To interrupt generator
(Capture Event)
(Capture Event)
C
C
C
C
C
S
C
To interrupt generator
(Speed Error Event)
Decreasing Speed
C
Decreasing Speed
C
counting the number of clock cycles issued by the
Incremental Encoder Interface (Encoder Clock)
during a fixed time window (refer to
The tachogenerator has a much lower ppr rate
than the encoder (typically factor 10). In this con-
text, it is more meaningful to measure the period
between Tacho Captures (i.e. relevant transitions
of the incoming signals). Accuracy is imposed by
the reference clock, i.e. the CPU clock (refer to
Figure
C
99).
C
C
C
S
Figure
C
100).
C