Z8 Encore! XP® F08xA Series
Product Specification
63
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Select either the rising edge or falling edge of the comparator output signal for the
count. This also sets the initial logic level (High or Low) for the Timer Output
alternate function. However, the Timer Output function is not required to be
enabled.
2. Write to the Timer High and Low Byte registers to set the starting count value. This
action only affects the first pass in COMPARATOR COUNTER mode. After the first
timer Reload in COMPARATOR COUNTER mode, counting always begins at the
reset value of 0001H. Generally, in COMPARATOR COUNTER mode the Timer
High and Low Byte registers must be written with the value 0001H.
3. Write to the Timer Reload High and Low Byte registers to set the Reload value.
4. If appropriate, enable the timer interrupt and set the timer interrupt priority by writing
to the relevant interrupt registers.
5. If using the Timer Output function, configure the associated GPIO port pin for the
Timer Output alternate function.
6. Write to the Timer Control register to enable the timer.
In COMPARATOR COUNTER mode, the number of comparator output transitions since
the timer start is given by the following equation:
Comparator Output Transitions = Current Count Value – Start Value
PWM SINGLE OUTPUT Mode
In PWM SINGLE OUTPUT mode, the timer outputs a Pulse-Width Modulator (PWM)
output signal through a GPIO Port pin. The timer input is the system clock. The timer first
counts up to the 16-bit PWM match value stored in the Timer PWM High and Low Byte
registers. When the timer count value matches the PWM value, the Timer Output toggles.
The timer continues counting until it reaches the Reload value stored in the Timer Reload
High and Low Byte registers. Upon reaching the Reload value, the timer generates an
interrupt, the count value in the Timer High and Low Byte registers is reset to 0001Hand
counting resumes.
If the TPOLbit in the Timer Control register is set to 1, the Timer Output signal begins as
a High (1) and transitions to a Low (0) when the timer value matches the PWM value. The
Timer Output signal returns to a High (1) after the timer reaches the Reload value and is
reset to 0001H.
If the TPOLbit in the Timer Control register is set to 0, the Timer Output signal begins as
a Low (0) and transitions to a High (1) when the timer value matches the PWM value. The
Timer Output signal returns to a Low (0) after the timer reaches the Reload value and is
reset to 0001H.
The steps for configuring a timer for PWM Single Output mode and initiating the PWM
operation are as follows:
PS024705-0405
P R E L I M I N A R Y
Timers
ZILOG [ ZILOG, INC. ]
