Z8F0113HJ005EG Datasheet, PDF (94/245 Pages) Zilog, Inc. – High-Performance 8-Bit Microcontrollers

Z8 Encore! XP^® F0823 Series
Product Specification
79
input capture and reload events. If appropriate, configure the timer interrupt to be gen-
erated 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 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)
CAPTURE RESTART Mode
In CAPTURE RESTART Mode, the current timer count value is recorded when the
acceptable external Timer Input transition occurs. The capture count value is written to the
Timer PWM High and Low Byte registers. The timer input is the system clock. The TPOL
bit in the Timer Control Register determines if the capture occurs on a rising edge or a fall-
ing edge of the Timer Input signal. When the capture event occurs, an interrupt is gener-
ated and the count value in the Timer High and Low Byte registers is reset to 0001H and
counting resumes. The INPCAP bit in TxCTL1 Register is set to indicate the timer inter-
rupt is because of an input capture event.
If no capture event occurs, the timer counts up to the 16-bit compare value stored in the
Timer Reload High and Low Byte registers. Upon 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. The INPCAP bit in TxCTL1 Register is cleared to indicate
the timer interrupt is not caused by an input capture event.
Observe the following steps to configure a timer for CAPTURE RESTART Mode and ini-
tiating the count:
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 TMODEHI bit 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 (typi-
cally 0001H).
3. Write to the Timer Reload High and Low Byte registers to set the reload value.
PS024315-1011
PRELIMINARY
Operation