Z8F042ASJ020EG2156 Datasheet, PDF (92/280 Pages) Zilog, Inc. – High-Performance 8-Bit Microcontrollers

Z8 Encore! XP^® F082A Series
Product Specification
76
count value in the Timer High and Low Byte registers is reset to 0001h and counting
resumes.
If the TPOL bit 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 TPOL bit 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.
Observe the following steps for configuring a timer for PWM Single Output Mode and ini-
tiating the PWM operation:
1. Write to the Timer Control Register to:
– Disable the timer
– Configure the timer for PWM Single Output Mode
– Set the prescale value
– Set the initial logic level (High or Low) and PWM High/Low transition for the
Timer Output alternate function
2. Write to the Timer High and Low Byte registers to set the starting count value (typi-
cally 0001h). This only affects the first pass in PWM Mode. After the first timer reset
in PWM Mode, counting always begins at the reset value of 0001h.
3. Write to the PWM High and Low Byte registers to set the PWM value.
4. Write to the Timer Reload High and Low Byte registers to set the reload value (PWM
period). The reload value must be greater than the PWM value.
5. If appropriate, enable the timer interrupt and set the timer interrupt priority by writing
to the relevant interrupt registers.
6. Configure the associated GPIO port pin for the Timer Output alternate function.
7. Write to the Timer Control Register to enable the timer and initiate counting.
The PWM period is represented by the following equation:
PWM Period (s) = -------^R----^e---^l-^o---^a----^d----^V----^a---^l-^u---^e----^----^P----^r--^e---^s--^c---^a---^l-^e--------
System Clock Frequency (Hz)
If an initial starting value other than 0001h is loaded into the Timer High and Low Byte
registers, use the One-Shot Mode equation to determine the first PWM time-out period.
PS022828-0413
PRELIMINARY
Operation