Z8F4822AR020SG Datasheet, PDF (85/323 Pages) Zilog, Inc. – High Performance 8-Bit Microcontrollers

Z8 Encore! XP^® F64xx Series
Product Specification
65
– Disable the timer
– Configure the timer for CONTINUOUS Mode
– Set the prescale value
– 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), affecting only 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 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 1 Register to enable the timer and initiate counting.
In CONTINUOUS Mode, the system clock always provides the timer input. The timer
period is calculated using the following equation:
CONTINUOUS Mode Time-Out Period (s) = -------R----e---l--o---a--d-----V----a---l--u---e----^-----P---r--e---s--c---a--l--e--------
System Clock Frequency (Hz)
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 1 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.
Caution: 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
PS019924-0113
PRELIMINARY
Operation