Z8F0830HH020SG Datasheet, PDF (95/257 Pages) Zilog, Inc. – High-Performance 8-Bit Microcontrollers

Z8 Encore!^® F0830 Series
Product Specification
77
PWM Output High Time Ratio (%)
=
R-----e--l--o---a---d----V----a---l--u---e----–----P----W-----M-------V-----a--l--u---e-
Reload Value

100
If TPOL is set to 1, the ratio of the PWM output high time to the total period is represented
by:
PWM Output High Time Ratio (%) = --P---W------M-------V----a---l-u---e---  100
Reload Value
CAPTURE Mode
In CAPTURE Mode, the current timer count value is recorded when the appropriate exter-
nal 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 falling edge
of the timer input signal.
When the capture event occurs, an interrupt is generated and the timer continues counting.
The INPCAP bit in the TxCTL1 Register is set to indicate the timer interrupt because of an
input capture event.
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 inter-
rupt and continues counting. The INPCAP bit in the TxCTL1 Register clears, indicating
that the timer interrupt has not occurred because of an input capture event.
Observe the following steps for configuring a timer for CAPTURE Mode and initiating
the count:
1. Write to the Timer Control 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 (typi-
cally 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. Clearing these registers
allows user software to determine if interrupts were generated either by a capture
event or by a reload. If the PWM High and Low Byte registers still contain 0000H
after the interrupt, the interrupt were generated by a reload.
PS025113-1212
Operation