Z8 Encore! XP® F08xA Series
Product Specification
68
The steps for configuring a timer for CAPTURE RESTART mode and initiating the count
are as follows:
1. Write to the Timer Control register to:
–
–
Disable the timer
Configure the timer for CAPTURE RESTART mode. Setting the mode also
involves writing to TMODEHIbit in TxCTL1 register.
–
–
Set the prescale value.
Set the Capture edge (rising or falling) for the Timer Input.
2. Write to the Timer High and Low Byte registers to set the starting count value
(typically 0001H).
3. Write to the Timer Reload High and Low Byte registers to set the Reload value.
4. Clear the Timer PWM High and Low Byte registers to 0000H. This allows user
software to determine if interrupts were generated by either a capture event or a
reload. If the PWM High and Low Byte registers still contain 0000Hafter the
interrupt, the interrupt was generated by a Reload.
5. 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 capture and reload events. If appropriate, configure the timer interrupt to be
generated only at the input capture event or the reload event by setting TICONFIG
field of the TxCTL1 register.
6. Configure the associated GPIO port pin for the Timer Input alternate function.
7. Write to the Timer Control register to enable the timer and initiate counting.
In CAPTURE mode, the elapsed time from timer start to Capture event can be calculated
using the following equation:
(Capture Value – Start Value) × Prescale
Capture Elapsed Time (s) = ----------------------------------------------------------------------------------------------------
System Clock Frequency (Hz)
COMPARE Mode
In COMPARE mode, the timer counts up to the 16-bit maximum Compare value stored in
the Timer Reload High and Low Byte registers. The timer input is the system clock. Upon
reaching the Compare value, the timer generates an interrupt and counting continues (the
timer value is not reset to 0001H). Also, if the Timer Output alternate function is enabled,
the Timer Output pin changes state (from Low to High or from High to Low) upon Com-
pare.
If the Timer reaches FFFFH, the timer rolls over to 0000H and continue counting.
The steps for configuring a timer for COMPARE mode and initiating the count are as fol-
lows:
PS024705-0405
P R E L I M I N A R Y
Timers
ZILOG [ ZILOG, INC. ]
