Z8F082ASH020SC datasheet(78/244 Pages) ZILOG

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PS024705-0405

P R E L I M I N A R Y

Timers

Z8 Encore! XP® F08xA Series

Product Specification

it is appropriate to have the Timer Output make a state change at a One-Shot time-out

(rather than a single cycle pulse), first set the TPOL bit in the Timer Control Register to

the start value before enabling ONE-SHOT mode. After starting the timer, set TPOL to the

opposite bit value.

The steps for configuring a timer for ONE-SHOT mode and initiating the count are as fol-

lows:

1. Write to the Timer Control register to:

–

Disable the timer

–

Configure the timer for ONE-SHOT mode.

–

Set the prescale value.

–

Set the initial output level (High or Low) if using the Timer Output alternate

function.

2. Write to the Timer High and Low Byte registers to set the starting count value.

3. Write to the Timer Reload High and Low Byte registers to set the Reload value.

4. If appropriate, enable the timer interrupt and set the timer interrupt priority by writing

to the relevant interrupt registers.

5. If using the Timer Output function, configure the associated GPIO port pin for the

Timer Output alternate function.

6. Write to the Timer Control register to enable the timer and initiate counting.

In ONE-SHOT mode, the system clock always provides the timer input. The timer period

is given by the following equation:

CONTINUOUS Mode

In CONTINUOUS mode, the timer counts up to the 16-bit Reload value stored in the

Timer Reload High and Low Byte registers. The timer input is the system clock. 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. Also, if the Timer

Output alternate function is enabled, the Timer Output pin changes state (from Low to

High or from High to Low) at timer Reload.

The steps for configuring a timer for CONTINUOUS mode and initiating the count are as

follows:

1. Write to the Timer Control register to:

–

Disable the timer

–

Configure the timer for CONTINUOUS mode.

–

Set the prescale value.

One-Shot Mode Time-Out Period (s)

Reload Value

Start Value

–

() Prescale

System Clock Frequency (Hz)

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