Z8F0830HH020SG Datasheet, PDF (94/257 Pages) Zilog, Inc. – High-Performance 8-Bit Microcontrollers

Z8 Encore!^® F0830 Series
Product Specification
76
Observe the following steps for configuring a timer for PWM DUAL OUTPUT Mode and
for initiating the PWM operation:
1. Write to the Timer Control Register to:
– Disable the timer
– Configure the timer for PWM DUAL OUTPUT Mode; setting the mode also
involves writing to TMODEHI bit in the TxCTL1 Register
– 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 write 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 PWM Control Register to set the PWM deadband delay value. The dead-
band delay must be less than the duration of the positive phase of the PWM signal (as
defined by the PWM High and Low Byte registers). It must also be less than the dura-
tion of the negative phase of the PWM signal (as defined by the difference between
the PWM registers and the Timer Reload registers).
5. 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.
6. If appropriate, enable the timer interrupt and set the timer interrupt priority by writing
to the relevant interrupt registers.
7. Configure the associated GPIO port pin for the timer output and timer output comple-
ment alternate functions. The timer output complement function is shared with the
timer input function for both timers. Setting the timer mode to DUAL PWM will auto-
matically switch the function from timer-in to timer-out complement.
8. 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, the ONE-SHOT Mode equation determines the first PWM time-out period.
If TPOL is set to 0, the ratio of the PWM output high time to the total period is represented
by:
PS025113-1212
Operation