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CHAPTER 11 16-BIT RELOAD TIMER
MB90560 series
11.1 Overview of the 16-Bit Reload Timer
The 16-bit reload timer is synchronized with three types of internal clocks for counting
down in internal clock mode, and it counts down by detecting an optional edge input to
the external pin in event counter mode.
This timer defines that an underflow condition results when the counter value changes
from “0000
H
“ to “FFFF
H
”. Thus, an underflow will occur after an interval of [reload
register setting value + 1] counts.
Either of two modes can be selected for counting. In reload mode, the value set for the
count is reloaded to repeat counting for an underflow. In single-shot mode, the
counting is stopped with an underflow.
The counter underflow allows the occurrence of an interrupt and coordination with the
extended intelligent I/O service (EI
2
OS).
The MB90560 series 16-bit reload timer has two built-in channels.
I
16-bit reload timer operating modes
Table 11.1-1 lists the operating modes of the 16-bit reload timer.
Table 11.1-1 16-bit reload timer operating modes
I
Internal clock mode
Internal clock mode allows selection of one of three types of internal clock for the following
operations:
G
Software trigger operation
When “1” is written to the TRG bit of the timer control status register (TMCSR), counting starts.
Trigger input by the TRG bit is always valid for external trigger input as well as for external gate
input.
G
External trigger operation
When selected edges (rising, falling, and both edges) are input to the TIN0 and TIN1 pins,
counting starts.
G
External gate input operation
While the selected signal level (“L” or “H”) is being input to TIN0 and TIN1 pins, counting
continues.
Clock mode
Counter operation
Operation of 16-bit reload timer
Internal clock mode
Reload mode
Software trigger operation
External trigger operation
External gate input operation
One-shot mode
Event count mode (external
clock mode)
Reload mode
Software trigger operation
One-shot mode