st7pmc2s6 STMicroelectronics, st7pmc2s6 Datasheet - Page 227

• Manufacturer Part Number: st7pmc2s6
• Description: 8-bit Mcu For Automotive With Nested Interrupts, Flash, 10-bit Adc, Brushless Motor Control, 5 Timers, Spi, Linsci?
• Manufacturer: STMicroelectronics

ST7MC1K2-Auto, ST7MC1K6-Auto, ST7MC2S4-Auto, ST7MC2S6-Auto
Speed measurement mode
Motor speed can be measured using two methods depending on sensor type: period measurement or
pulse counting. Typical sensor handling is described here.
Incremental encoders allows accurate speed measurement by providing a large number of pulses per
revolution (ppr) with ppr rates up to several thousands; the higher the ppr rate, the higher the resolution.
The proposed method consists of 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 context, it is
more meaningful to measure the period between tacho captures (that is, relevant transitions of the
incoming signals). Accuracy is imposed by the reference clock, that is, the CPU clock (refer to
Figure
Figure 100. Tachogenerator period acquisition using MTIM timer
Figure 101. Encoder clock frequency measure using MTIM timer
software or real time clack
Capture (triggered by
C
MTIM counter value
100).
C
MTIM counter
Comparator
Encoder clock
Interrupts
Compare
capture
output
Tacho
Interrupts
value
value
to interrupt generator
(capture event)
to interrupt generator
(capture event)
C
C
C
C
C
S
to interrupt generator
C
(speed error event)
C
Decreasing speed
Decreasing speed
C
Figure
C
101).
C
C
On-chip peripherals
C
S
C
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C