eZ80L92 MCU
Product Specification
80
Table 30. PRT CONTINUOUS Mode Operation Example
Parameter
Control Register(s)
TMRx_CTL[0]
TMRx_CTL[1]
TMRx_CTL[3:2]
TMRx_CTL[4]
TMRx_CTL[6]
Value
PRT Enabled
1
1
Reload and Restart Enabled
PRT Clock Divider = 4
CONTINUOUS Mode
PRT Interrupt Enabled
PRT Reload Value
00b
1
1
{TMRx_RR_H, TMRx_RR_L}
0004h
Reading the Current Count Value
The CPU is capable of reading the current count value while the timer is running. This
Read event does not affect timer operation. The High byte of the current count value is
latched during a Read of the Low byte.
Timer Interrupts
The timer interrupt flag, PRT_IRQ, is set to 1 whenever the timer reaches its end-of-count
value, 0000h, in SINGLE PASS mode, or when the timer reloads the start value in
CONTINUOUS mode. The interrupt flag is only set when the timer reaches 0000h (or
reloads) from 0001h. The timer interrupt flag is not set to 1 when the timer is loaded with
the value 0000h, which selects the maximum time-out period.
The CPU can be programmed to poll the PRT_IRQ bit for the time-out event. Alterna-
tively, an interrupt service request signal can be sent to the CPU by setting IRQ_EN to 1.
Then, when the end-of-count value, 0000h, is reached and PRT_IRQ is set to 1, an
interrupt service request signal is passed to the CPU. PRT_IRQ is cleared to 0 and the
interrupt service request signal is inactivated whenever the CPU reads from the timer con-
trol registers, TMRx_CTL.
Timer Input Source Selection
Timers 0–3 feature programmable input source selection. By default, the input is taken
from the ZLP12840’s system clock. Alternatively, Timers 0–3 can take their input from
port input pins PB0 (Timers 0 and 2) or PB1 (Timers 1 and 3). Timers 0–3 can also use the
Real-Time Clock clock source (50, 60, or 32768 Hz) as their clock sources. When the
timer clock source is the Real-Time Clock signal, the timer decrements on the second
rising edge of the system clock following the falling edge of the RTC_XOUT pin. The
input source for these timers is set using the Timer Input Source Select register.
PS013015-0316
Programmable Reload Timers
ZILOG [ ZILOG, INC. ]
