60
RPM
TeethNumber ToothPeriod
u
Angle Functions
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SPNU563A–March 2018
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High-End Timer (N2HET) Module
23.3.2.5 Range of Operations
23.3.2.5.1 Intrinsic HWAG Limitation
The following factors limit the HWAG:
• SYSCLK
• PCNT counter (overflow)
• Number of teeth
• Angle step
These factors will influence the engine speed range (RPM limitation) and the maximum accuracy of the
angle steps (wheel limitation).
• RPM limitation
The toothed wheel speed is limited by the period counter (PCNT) and the angle step for a given
SYSCLK.
RPM minimum is related to PCNT overflow and SYSCLK.
Maximum PCNT value × SYSCLK = Maximum tooth period
PCNT is a 24-bit counter based on SYSCLK.
RPM maximum is related to the angle step and SYSCLK.
Minimum tooth period > Step Width × SYSCLK
The angle ticks period could not be inferior to the SYSCLK.
Example: The toothed wheel is a 60-2, SYSCLK is 50 Mhz (20 ns), and step width is 512:
RPM minimum ≥ 16 777 215 × 20 ns = 335.5443 ms ≥ ~3 RPM
RPM maximum ≥ 512 × 20 ns = 10.24 µs ≥ 97 656 RPM
NOTE: With a 60-2 toothed wheel, the tooth period is the reverse of the RPM number.
• Wheel Limitation
The HWAG is limited by the number of teeth and the increments in a revolution.
The maximum number of teeth is 256. This limits the number of increments per revolution to 512 steps
× 256 teeth = 131 072 angle increments.
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