ZUSBOPTSC01ZACG datasheet(92/282 Pages) ZILOG

92 / 282 page

PS022827-1212

P R E L I M I N A R Y

Operation

Z8 Encore! XP® F082A Series

Product Specification

The frequency of the comparator output signal must not exceed one-fourth the system

clock frequency. Further, the high or low state of the comparator output signal pulse must

be no less than twice the system clock period. A shorter pulse may not be captured.

After 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.

Observe the following steps for configuring a timer for COMPARATOR COUNTER

Mode and initiating the count:

1. Write to the Timer Control Register to:

–

Disable the timer.

–

Configure the timer for COMPARATOR COUNTER Mode.

–

Select either the rising edge or falling edge of the comparator output signal for the

count. This also sets the initial logic level (High or Low) for the Timer Output

alternate function. However, the Timer Output function is not required to be

enabled.

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

action only affects the first pass in COMPARATOR COUNTER Mode. After the first

timer Reload in COMPARATOR COUNTER Mode, counting always begins at the

reset value of 0001H. Generally, in COMPARATOR COUNTER Mode the Timer

High and Low Byte registers must be written with the value 0001H.

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.



In COMPARATOR COUNTER Mode, the number of comparator output transitions since

the timer start is computed via the following equation:

Caution:

Comparator Output Transitions

Current Count Value

Start Value

–

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