MAC7200 datasheet(789/976 Pages) FREESCALE

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Functional Description

MAC7200 Microcontroller Family Reference Manual, Rev. 2

Freescale Semiconductor

711

32.13.1.1.10 Windowed Programmable Time Accumulation (WPTA) Mode

The WPTA mode accumulates the sum of the total high time or low time of an input signal over a

programmable interval (time window).

The prescaler bits UCPRE[1:0] in UCCRn register define the increment rate of the internal counter.

When a match occurs between register A and the selected timebase, the internal counter is cleared and it

is ready to start counting. The internal counter is used as a time accumulator, i.e., it counts up when the

input signal has the same polarity of EDPOL bit in UCCRn register and does not count otherwise. When

a match occurs in comparator B, the internal counter is disabled regardless of the input signal polarity and

the FLAG bit is set. At the same time the content of UCCNTn is transferred to register A2. Reading

registers UCCNTn or A2 returns the high or low time of the input signal,

Note that UCCNTn is stable only outside the time window defined from A1 to B1 matches, otherwise its

contents reflects a count in progress and not the final value. Alternatively to UCCNTn register A2 returns

the latest available measurement. Since this register is updated only at comparator B matches it always

contains stable and up-to-date data. In this mode this register is accessible through the alternate register

address ALTAn.

Figure 32-29 shows how the Unified Channel can be used to accumulate high time.

Figure 32-29. Windowed Programmable Time Accumulation example

32.13.1.1.11 Modulus Counter (MC) Mode

The MC mode can be used to provide a time base for a counter bus or as a general purpose timer.

MODE[0] bit selects internal or external clock source when cleared or set, respectively. When external

clock is selected, the input signal pin is used as the source and the triggering polarity edge is selected by

the EDPOL and EDSEL in the UCCRn register.

$FFFFFF

$000000

Time accumulator (UCCNT)

B1 Match

selected counter bus

$001500

A1 value2

$001500

$000100 $000100

input signal1

$004200

$003000

B1 Match

B1 value3

$001500

$004200

$000100

A1 Match

A1 B1 write

A1 Match

A1 B1 write

$003000

$004200

FLAG set event

Notes: 1. After the input filter

EDPOL = 1

2. UCAn = A1

3. UCBn = B1

$003000

A2 value4

UCCNTn

4 ALTAn = A2

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