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eTPU software design

AN2577

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eTPU software design

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 can be obtained from your ST representative.

4.1

Host setup

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 Angle Mode bit in the ETPUTBCR must be set.

The TCRCLK Filter Mode must be setup.

Initial Channel 0 parameters must be written.

Channel 0 must be initialized.

The TCR2 Clock Source in the ETPUTBCR must be set for rising or falling edges

to match the IPAC setting for the tooth in Channel 0.

The last step may be delayed until Channel 0 has confirmed synchronization.

4.2

State machine description

Table 1 shows a simplified state table for an angle clock system, similar to the

implementation in the reference design. The states are referenced in the following

description of an angle clock system implementation.

Table 1.

Angle clock system state

Reference

name

Action

Exit

condition

InitializeCrank

TICKS = TicksPerToot - 1

If ActiveEdge

ToothCount = 0

CrankStatus = Stall;

First_edge

CrankStatus = WaitingGap

If timeout (StallTimer)

StallTimer = StallPeriod at startpoint Time(activeEdge)

If ActiveEdge

ToothTime = Time(ActiveEdge)

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