Z8F3201PM020SC datasheet(78/246 Pages) ZILOG

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PS017610-0404

Timers

Z8F640x/Z8F480x/Z8F320x/Z8F240x/Z8F160x

Z8 Encore!®

–

If using the Timer Output alternate function, set the initial output level (High or

Low).

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

0001H

). This only affects the first pass in Continuous mode. After the first timer

Reload in Continuous 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. If desired, 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 Continuous mode, the system clock always provides the timer input. The timer period is

given by the following equation:

If an initial starting value other than 0001H is loaded into the Timer High and Low Byte

registers, the One-Shot mode equation must be used to determine the first time-out period.

Counter Mode

In Counter mode, the timer counts input transitions from a GPIO port pin. The timer input

is taken from the GPIO Port pin Timer Input alternate function. The TPOL bit in the Timer

Control Register selects whether the count occurs on the rising edge or the falling edge of

the Timer Input signal. In Counter mode, the prescaler is disabled.

The input frequency of the Timer Input signal must not exceed one-fourth

the system clock frequency.

Upon reaching the Reload value stored in the Timer Reload High and Low Byte registers,

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 Counter mode and initiating the count are as follows:

1. Write to the Timer Control register to:

–

Disable the timer

–

Configure the timer for Counter mode.

Continuous Mode Time-Out Period (s)

Reload Value

Prescale

System Clock Frequency (Hz)

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Caution:

Z8F3201PM020SC Datasheet(PDF) 78 Page - Zilog, Inc.

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