EZ80F91MCU Datasheet, PDF (150/396 Pages) Zilog, Inc. – eZ80Acclaim-TM Flash Microcontrollers

eZ80F91 MCU
Product Specification
131
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 EOC bit for the time-out event. Alterna-
tively, an interrupt service request signal can be sent to the CPU by setting the
TMRx_IER[EOC] bit to 1. Then, when the end-of-count value (0000h) is reached
and the EOC bit is set to 1, an interrupt service request signal is passed to the
CPU. The interrupt service request signal is deactivated by an CPU Read of the
timer interrupt identification register, TMRx_IIR. All bits in that register are reset by
the Read.
The response of the CPU to this interrupt service request is a function of the
CPU’s interrupt enable flag, IEF1. For more information about this flag, refer to the
eZ80^® CPU User Manual (UM0077), which is available on zilog.com.
Timer Input Source Selection
Timers 0–3 feature programmable input source selection. By default, the input is
taken from the eZ80F91’s system clock. The timers can also use the Real-Time
Clock source (50, 60, or 32768 Hz) as their clock sources. The input source for
these timers is set using the timer control register. (TMRx_CTL[CLK_SEL])
Timer Output
The timer count can be directed to the GPIO output pins if required. To enable the
Timer Out feature, the GPIO port pin must be configured as an output and for
alternate functions. The GPIO output pin toggles each time the timer reaches its
end-of-count value. In CONTINUOUS mode operation, enabling the Timer Output
feature results in a Timer Output signal period that is twice the timer time-out
period. Examples of the Timer Output operation are illustrated in Figure 28 and
Table 52. The initial value for the timer output is zero.
Logic to support timer output exists in all timers, but for the eZ80F91 device, only
Timer 0 and 2 route the actual timer output to the pins. Because Timer 3 uses the
T_OUT pins for PWMxN signals, the timer outputs are not available when using
complementary PWM outputs. See Table 53 for details.
PS019209-0504
PRELIMINARY
Programmable Reload Timers