Maxim Integrated MAXQ622 - Manual (Page 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)
TBC (POSITION A)
TBCS, TBCR =
TBC (POSITION B)
TBCS, TBCR =
10 (SET)
10 (SET)
01 (RESET)
01 (RESET)
11 (TOGGLE)
11 (TOGGLE)