PC912XDP512F0MPVR datasheet(360/1348 Pages) FREESCALE

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Chapter 7 Enhanced Capture Timer (S12ECT16B8CV2)

MC9S12XDP512 Data Sheet, Rev. 2.21

360

Freescale Semiconductor

7.4.1.5

Precision Timer

By enabling the PRNT bit of the TSCR1 register, the performance of the timer can be enhanced. In this

case, it is possible to set additional prescaler settings for the main timer counter and modulus down counter

and enhance delay counter settings compared to the settings in the present ECT timer.

7.4.1.6

Flag Clearing Mechanisms

The ﬂags in the ECT can be cleared one of two ways:

1. Normal ﬂag clearing mechanism (TFFCA = 0)

Any of the ECT ﬂags can be cleared by writing a one to the ﬂag.

2. Fast ﬂag clearing mechanism (TFFCA = 1)

With the timer fast ﬂag clear all (TFFCA) enabled, the ECT ﬂags can only be cleared by accessing

the various registers associated with the ECT modes of operation as described below. The ﬂags

cannot be cleared via the normal ﬂag clearing mechanism. This fast ﬂag clearing mechanism has

the advantage of eliminating the software overhead required by a separate clear sequence. Extra

care must be taken to avoid accidental ﬂag clearing due to unintended accesses.

— Input capture

A read from an input capture channel register causes the corresponding channel ﬂag, CxF, to

be cleared in the TFLG1 register.

— Output compare

A write to the output compare channel register causes the corresponding channel flag, CxF, to

be cleared in the TFLG1 register.

— Timer counter

Any access to the TCNT register clears the TOF flag in the TFLG2 register.

— Pulse accumulator A

Any access to the PACN3 and PACN2 registers clears the PAOVF and PAIF flags in the

PAFLG register.

— Pulse accumulator B

Any access to the PACN1 and PACN0 registers clears the PBOVF flag in the PBFLG register.

— Modulus down counter

Any access to the MCCNT register clears the MCZF flag in the MCFLG register.

7.4.2

Reset

The reset state of each individual bit is listed within the register description section (Section 7.3, “Memory

Map and Register Deﬁnition”) which details the registers and their bit-ﬁelds.

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