Z8F021ASH020SC datasheet(87/276 Pages) ZILOG

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PS022815-0206

Timers

Z8 Encore! XP® 4K Series

Product Specification

The steps for configuring a timer for PWM SINGLE 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 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

(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 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:

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.

If TPOL is set to 0, the ratio of the PWM output High time to the total period is repre-

sented by:

If TPOL is set to 1, the ratio of the PWM output High time to the total period is repre-

sented by:

PWM Period (s)

Reload Value Prescale

System Clock Frequency (Hz)

----------------------------------------------------------------------------

PWM Output High Time Ratio (%)

Reload Value PWM Value

–

Reload Value

------------------------------------------------------------------------ 100

PWM Output High Time Ratio (%)

PWM Value

Reload Value

---------------------------------- 100

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