Z8F6421PM020SC Datasheet, PDF (101/299 Pages) Zilog, Inc. – High Performance 8-Bit Microcontrollers Z8 Encore-R 64K Series

Z8 Encore!^® 64K Series
Product Specification
81
Timer Input signal. When the Capture event occurs, an interrupt is generated and the timer
continues counting.
The timer continues counting up to the 16-bit Reload value stored in the Timer Reload
High and Low Byte registers. Upon reaching the Reload value, the timer generates an
interrupt and continues counting.
The steps for configuring a timer for CAPTURE mode and initiating the count are as fol-
lows:
1. Write to the Timer Control 1 register to:
– Disable the timer
– Configure the timer for CAPTURE mode.
– 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 0000H after the
interrupt, then the interrupt was generated by a Reload.
5. If desired, enable the timer interrupt and set the timer interrupt priority by writing to
the relevant interrupt registers.
6. Configure the associated GPIO port pin for the Timer Input alternate function.
7. Write to the Timer Control 1 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 Elapsed Time (s) = ⁽---C----a---p----t--u---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)
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.
PS019915-1005
Timers