Z8F0113HJ005EG Datasheet, PDF (96/245 Pages) Zilog, Inc. – High-Performance 8-Bit Microcontrollers

Z8 Encore! XP^® F0823 Series
Product Specification
81
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 COMPARE Mode, the system clock always provides the timer input. The compare time
can be calculated by the following equation:
COMPARE Mode Time (s) = -^--^C----^o---^m----^p---^a---^r--^e-----^V---^a---^l--^u---^e----^–----^S----^t-^a---^r--^t---^V----^a---^l-^u---^e----^---^----^P---^r--^e---^s---^c---^a---^l-^e-
System Clock Frequency (Hz)
GATED Mode
In GATED Mode, the timer counts only when the Timer Input signal is in its active state
(asserted), as determined by the TPOL bit in the Timer Control Register. When the Timer
Input signal is asserted, counting begins. A timer interrupt is generated when the Timer
Input signal is deasserted or a timer reload occurs. To determine if a Timer Input signal
deassertion generated the interrupt, read the associated GPIO input value and compare to
the value stored in the TPOL bit.
The timer counts up to the 16-bit reload value stored in the Timer Reload High and Low
Byte registers. The timer input is the system clock. When reaching the reload value, the
timer generates an interrupt, the count value in the Timer High and Low Byte registers is
reset to 0001H and counting resumes (assuming the Timer Input signal remains asserted).
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 reset.
Observe the following steps to configure a timer for GATED Mode and to initiate the
count:
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 TxCTL1 Register.
PS024315-1011
PRELIMINARY
Operation