AN2897 Freescale Semiconductor / Motorola, AN2897 Datasheet - Page 18

• Manufacturer Part Number: AN2897
• Description: Using the eTPU Angle Clock
• Manufacturer: Freescale Semiconductor / Motorola

eTPU Software Design
3.5
If the tooth circuit fails and the failure is detected by the host, the software may implement a limp home
strategy. The eTPU Angle Clock provides a method to disconnect the Angle Clock system from the
Channel 0 input so that spurious signals from the tooth circuit will not disrupt the limp home system. In
that event, the host may configure the eTPU such that Channel 0 continues to monitor the tooth circuit for
diagnostic purpose. See the Reference Manual for details.
4
The software shown below is taken from an Automotive Reference Design which demonstrates the
operation and application of the eTPU Angle Clock in a practical automotive engine control system. Code
that is directly copied is displayed in Courier New font. The Reference Design is free to customers
and can be obtained from Byte Craft, Ash Ware, or your Freescale representative.
4.1
The host must setup the registers and parameters in the eTPU to enable the Angle Clock. In addition to the
setup required for any eTPU operation, use of the Angle Clock requires the following steps.
The last step may be delayed until Channel 0 has confirmed synchronization.
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a) The Angle Mode bit in the ETPUTBCR must be set.
b) The TCRCLK Filter Mode must be setup.
c) Initial Channel 0 parameters must be written.
d) Channel 0 must be initialized.
e) The TCR2 Clock Source in the ETPUTBCR must be set for rising or falling edges to match
Tooth Circuit Failure
eTPU Software Design
Host Setup
the IPAC setting for the tooth in Channel 0.
Using the eTPU Angle Clock, Rev. 0
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