HT46R232/HT46C232
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Timer/Event Counter 0
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Timer/Event Counter 1
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PFD Source Option
In the case of timer/event counter OFF condition, writing
data to the timer/event counter preload register also re-
loads that data to the timer/event counter. But if the
timer/event counter is turn on, data written to the
timer/event counter is kept only in the timer/event coun-
ter preload register. The timer/event counter still contin-
ues its operation until an overflow occurs.
To enable the counting operation, the Timer ON bit
(T0ON: bit 4 of TMR0C; T10N: bit 4 of TMR1C) should
be set to 1. In the pulse width measurement mode, the
T0ON/T1ON is automatically cleared after the measure-
ment cycle is completed. But in the other two modes, the
T0ON/T1ON can only be reset by instructions. The
overflow of the Timer/Event Counter 0/1 is one of the
wake-up sources and can also be applied to a PFD (Pro-
grammable Frequency Divider) output at PA3 by op-
tions. Only one PFD (PFD0 or PFD1) can be applied to
PA3 by options. If PA3 is set as PFD output, there are
two types of selections; One is PFD0 as the PFD output,
the other is PFD1 as the PFD output. PFD0, PFD1 are
the timer overflow signals of the Timer/Event Counter 0,
Timer/Event Counter 1 respectively. No matter what the
operation mode is, writing a 0 to ET0I or ET1I disables
the related interrupt service. When the PFD function is
selected, executing ²SET [PA].3² instruction to enable
PFD output and executing ²CLR [PA].3² instruction to
disable PFD output.
When the timer/event counter (reading TMR0/TMR1) is
read, the clock is blocked to avoid errors, as this may re-
sults in a counting error. Blocking of the clock should be
taken into account by the programmer. It is strongly rec-
ommended to load a desired value into the TMR0/TMR1
register first, before turning on the related timer/event
counter, for proper operation since the initial value of
TMR0/TMR1 is unknown. Due to the timer/event
scheme, the programmer should pay special attention
on the instruction to enable then disable the timer for the
first time, whenever there is a need to use the
timer/event function, to avoid unpredictable result. After
this procedure, the timer/event function can be operated
normally.
Rev. 1.50
15
January 21, 2009
HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
