Maxim-integrated MAXQ622 Manual do Utilizador descarregar pdf (Página 119)

MAXQ612/MAXQ622 User’s Guide

Maxim Integrated 7-5

7.1.5 Timer B Mode: PWM Output Function

The PWM output function is enabled whenever the TBCS:TBCR bit pair is nonzero. Table 7-2 shows how these bits

define a certain output function.

When the PWM output function is configured to the reset mode, configuring TBC = 0000h disables the TBC compare

match reset operation. The timer will do one set on 0000h and never reset. When the PWM output function is configured

to the set mode, configuring TBC = TBR disables the TBC compare match set operation. The timer will do one reset

on TBR match and never set. When the PWM output function is configured to toggle, configuring TBC = 0000h or TBR

disables the toggle function.

When the timer is not running (TRB = 0), the initial output starting state of the TBB output is established as low or high,

respectively, if the reset function (TBCR = 1,TBCS = 0) or set function (TBCR = 0, TBCS = 1) is established. Invoking

the toggle function does not change the already defined starting state for TBB, thus a fixed high or low starting state

may be defined for the toggle mode by first passing through the set or reset mode. The initial starting state takes effect

on the pin when the timer is started (TRB = 1). Changing the output function to set or reset while the timer is running

does not affect the current output.

Figure 7-4. Timer B Clock Output Mode

Table 7-2. Timer B PWM Output Function

*The initial state for the toggle mode depends on the previous set or reset mode. This means that the TBCS:TBCR bits should be

configured to set or reset momentarily when changing from “Compare Disable” to “Compare Toggle Mode” to establish a specific

starting state.

EXFB TIMER B INTERRUPT

TOGGLE

TFB

150

TBA PIN

TBR

0000h

TBV

TRB

SYSTEM

CLOCK

PRESCALER

TBPS[2:0]

C/TB = 0

TBOE = 1

TBA FREQUENCY OUT = PRESCALED SYSTEM CLOCK/(2 x (TBR + 1))

FALLING

EDGE

TBB PIN

EXENB

TBCS:TBCR FUNCTION INITIAL STATE (TRB = 0)

00 None (Compare Disable) No change

01 (Reset) Reset on TBC Match, Set on 0000h Low

10 (Set) Set on TBC Match, Reset on TBR Match High

11 (Toggle) Toggle on TBC Match (except TBR or 0h) No change*

1 2 ... 114 115 116 117 118 119 120 121 122 123 124 ... 254 255

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