Z8F6421PM020SC Datasheet, PDF (97/299 Pages) Zilog, Inc. – High Performance 8-Bit Microcontrollers Z8 Encore-R 64K Series

Z8 Encore!^® 64K Series
Product Specification
77
out, first set the TPOL bit in the Timer Control 1 Register to the start value before begin-
ning ONE-SHOT mode. Then, after starting the timer, set TPOL to the opposite bit value.
The steps for configuring a timer for ONE-SHOT 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 ONE-SHOT mode
– Set the prescale value
– If using the Timer Output alternate function, set the initial output level (High or
Low)
2. Write to the Timer High and Low Byte registers to set the starting count value
3. Write to the Timer Reload High and Low Byte registers to set the Reload value
4. If desired, enable the timer interrupt and set the timer interrupt priority by writing to
the relevant interrupt registers
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 1 register to enable the timer and initiate counting
In ONE-SHOT mode, the system clock always provides the timer input. The timer period
is given by the following equation:
One-Shot Mode Time-Out Period (s) = ⁽---R----e---l--o---a---d----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)
CONTINUOUS Mode
In CONTINUOUS mode, 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. 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. 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 timer Reload.
The steps for configuring a timer for CONTINUOUS mode and initiating the count are as
follows:
1. Write to the Timer Control 1 register to:
– Disable the timer
– Configure the timer for CONTINUOUS mode
– Set the prescale value
PS019915-1005
Timers