Z8F4822AR020SG Datasheet, PDF (87/323 Pages) Zilog, Inc. – High Performance 8-Bit Microcontrollers

Z8 Encore! XP^® F64xx Series
Product Specification
67
If the TPOL bit in the Timer Control 1 Register is set to 1, the timer output signal begins
as a High (1) and then 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 1 Register is set to 0, the timer output signal begins
as a Low (0) and then 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 procedure for configuring a timer for PWM Mode and initiating the
PWM operation:
1. Write to the Timer Control 1 Register to:
– Disable the timer
– Configure the timer for PWM 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 1 Register to enable the timer and initiate counting.
The PWM period is calculated using 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, the ONE-SHOT Mode equation must be used to determine the first PWM time-
out period.
PS019924-0113
PRELIMINARY
Operation