Z8F0830HH020SG Datasheet, PDF (90/257 Pages) Zilog, Inc. – High-Performance 8-Bit Microcontrollers

Z8 Encore!^® F0830 Series
Product Specification
72
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 COUNTER Mode and for initiat-
ing the count:
1. Write to the Timer Control Register to:
– Disable the timer
– Configure the timer for COUNTER Mode
– Select either the rising edge or falling edge of the timer input signal for the count.
This selection 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
only affects the first pass in COUNTER Mode. After the first timer reload in COUN-
TER Mode, counting always begins at the reset value 0001H. In 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. Configure the associated GPIO port pin for the timer input alternate function.
6. If using the timer output function, configure the associated GPIO port pin for the timer
output alternate function.
7. Write to the Timer Control Register to enable the timer.
In COUNTER Mode, the number of timer input transitions is calculated with the follow-
ing equation:
Counter Mode Timer Input Transitions = Current Count Value – Start Value
COMPARATOR COUNTER Mode
In COMPARATOR COUNTER Mode, the timer counts the input transitions from the ana-
log comparator output. The TPOL bit in the Timer Control Register determines whether
the count occurs on the rising edge or the falling edge of the comparator output signal. In
COMPARATOR COUNTER Mode, the prescaler is disabled.
PS025113-1212
Operation