Z8F021ASH020SC datasheet(93/276 Pages) ZILOG

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PS022815-0206

Timers

Z8 Encore! XP® 4K Series

Product Specification

1. Write to the Timer Control register to:

–

Disable the timer

–

Configure the timer for GATED mode.

–

Set the prescale value.

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

these registers only affects the first pass in GATED mode. After the first timer reset in

GATED mode, counting always begins at the reset value of 0001H.

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

4. Enable the timer interrupt, if appropriate, and set the timer interrupt priority by writing

to the relevant interrupt registers. By default, the timer interrupt is generated for both

input deassertion and reload events. If appropriate, configure the timer interrupt to be

generated only at the input deassertion event or the reload event by setting TICONFIG

field of the TxCTL0 register.

5. Configure the associated GPIO port pin for the Timer Input alternate function.

6. Write to the Timer Control register to enable the timer.

7. Assert the Timer Input signal to initiate the counting.

CAPTURE/COMPARE Mode

In CAPTURE/COMPARE mode, the timer begins counting on the first external Timer

Input transition. The acceptable transition (rising edge or falling edge) is set by the TPOL

bit in the Timer Control Register. The timer input is the system clock.

Every subsequent acceptable transition (after the first) of the Timer Input signal captures

the current count value. The Capture value is written to the Timer PWM High and Low

Byte Registers. When the Capture event occurs, an interrupt is generated, the count value

in the Timer High and Low Byte registers is reset to 0001H, and counting resumes. The

INPCAP

bit in TxCTL0 register is set to indicate the timer interrupt is caused by an input

capture event.

If no Capture event occurs, the timer counts up to the 16-bit Compare value stored in the

Timer Reload High and Low Byte registers. Upon reaching the Compare value, the timer

generates an interrupt, the count value in the Timer High and Low Byte registers is reset to

0001H

and counting resumes. The INPCAP bit in TxCTL0 register is cleared to indicate

the timer interrupt is not because of an input capture event.

The steps for configuring a timer for CAPTURE/COMPARE mode and initiating the

count are as follows:

1. Write to the Timer Control register to:

–

Disable the timer

–

Configure the timer for CAPTURE/COMPARE mode.

–

Set the prescale value.

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