Freescale-semiconductor ColdFire MCF52210 Manual de usuario descargar pdf (Pagina 487)

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101

Pulse-Width Modulation (PWM) Module

MCF52211 ColdFire® Integrated Microcontroller Reference Manual, Rev. 2

Freescale Semiconductor 27-13

27.3 Functional Description

27.3.1 PWM Clock Select

There are four available clocks—clock A, B, SA (scaled A), and SB (scaled B)—all based on the internal

bus clock.

Clock A and B can be programmed to run at 1, 1/2,..., 1/128 times the internal bus clock. Clock SA and

SB use clock A and B respectively as an input and divide it further with a reloadable counter. The rates

available for clock SA and SB are programmable to run at clock A and B divided by 2, 4,..., or 512. Each

PWM channel has the capability of selecting one of two clocks, the prescaled clock (clock A or B) or the

scaled clock (clock SA or SB). The block diagram in Figure 27-14 shows the four different clocks and how

the scaled clocks are created.

PWM7IL

PWM channel 7 input polarity. If PWMSDN[SDNEN] is set, this bit sets the active level of the PWM 7 channel

0 PWM 7 input is active low

1 PWN 7 input is active high

SDNEN

PWM emergency shutdown enable. If set, the pin associated with PWM channel 7 is forced to input and the

emergency shutdown feature is enabled.

0 Emergency shutdown is disabled

1 Emergency shutdown is enabled

Table 27-13. PWMSDN Field Descriptions (continued)

Field Description

1 2 ... 482 483 484 485 486 487 488 489 490 491 492 ... 575 576

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Freescale-semiconductor ColdFire MCF52210 Manual de usuario Pagina 487

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