Z8F082ASH020SC Datasheet, PDF (83/244 Pages) Zilog, Inc. – Z8 Encore XP-R F08xA Series with eXtended Peripherals

Z8 Encore! XP^® F08xA Series
Product Specification
65
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 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.
The timer also generates a second PWM output signal Timer Output Complement. The
Timer Output Complement is the complement of the Timer Output PWM signal. A pro-
grammable deadband delay can be configured to time delay (0 to 128 system clock cycles)
PWM output transitions on these two pins from a low to a high (inactive to active). This
ensures a time gap between the deassertion of one PWM output to the assertion of its com-
plement.
The steps for configuring a timer for PWM Dual Output mode and initiating the PWM
operation are as follows:
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 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
(typically 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 PWM Control register to set the PWM dead band delay value. The
deadband 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
duration 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.
PS024705-0405
PRELIMINARY
Timers