Maxim-integrated MAXQ622 Manual do Utilizador descarregar pdf (Página 120)

MAXQ612/MAXQ622 User’s Guide

7-6 Maxim Integrated

7.1.5.1 Timer B Mode: Up-Counting PWM Output Mode

The 16-bit timer/counter with autoreload mode is used for the up-counting PWM output mode to produce edge-aligned

PWM output. In the 16-bit autoreload timer mode, the Timer B allows an optional external pin (TBB) triggered reload

event when the EXENB bit is configured to 1. The external input special function and the PWM output function can

be enabled at the same time, however the input special function changes slightly when the PWM output is enabled.

When the PWM output mode is enabled (TBCS:TBCR ≠ 00b) and the external pin input is enabled (EXENB = 1), the

detection of a output falling edge on TBB should still result in setting of the EXFB interrupt flag, but should not force

an autoreload. Note that the EXFB flag can be set independent of the state of the TRB bit (e.g., EXFB can still be set

on detection of a negative edge when TRB = 0). While it is most likely that TRB = 1 when EXFB is set, since TRB = 1

is required to enable the PWM output, a negative edge on the TBB pin while TRB = 0 can still result in setting of EXFB.

Using the standard GPI/O port controls to generate a negative edge when the PWM is not running, for instance, can

set EXFB. Example TBB output waveforms for the autoreload up-counting mode are shown in Figure 7-5.

Figure 7-5. Timer B PWM Output Waveforms (Up Count, DCEN = 0)

TBR

0000

TBC (POSITION B)

TBC (POSITION A)

TBCS, TBCR =

TBC (POSITION B)

TBCS, TBCR =

10 (SET)

01 (RESET)

11 (TOGGLE)

1 2 ... 115 116 117 118 119 120 121 122 123 124 125 ... 254 255

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Maxim-integrated MAXQ622 Manual do Utilizador Página 120