
1-66
1.12 Timer X and Timer Y
HARDWARE
7480 Group and 7481 Group User's Manual
1.12.4 Timer Mode and Event Count Mode
(1)
Operations in Timer Mode and Event Count Mode
Operations in the timer mode and the event count mode are explained with Figure 1.12.8.
Count Sources
In the timer mode and the event count mode, timer X or timer Y can select the following count
sources with the timer X or Y count source selection bits:
f(XIN)/2
f(XIN)/8
timer mode
f(XIN)/16
CNTR0 pin input (Timer X used)
CNTR1 pin input (Timer Y used)
Notes 1: In the event count mode, the inverted signal of input to a CNTR pin is used as the count
source when a CNTR edge selection bit of the edge polarity selection register is ‘1’.
2: In the event count mode, keep the frequency of the CNTR pin input used as the count
source f(XIN)/4 or less.
Writes to and Reads from Timers
When ‘TL (000016 through FFFF16)’ is written to a timer, the following different operations are
performed depending on the state of the timer X or Y write control bit:
In the ‘0’ state of the timer X or Y write control bit, the ‘TL’ is set in both the timer latch and the
timer ( in Figure 1.12.8).
In the ‘1’ state of the timer X or Y write control bit, the ‘TL’ is set in the timer latch only.
Also, the contents of the timer can be read by a read operation.
Count Operation
When the timer X or Y stop control bit of the timer XY control register is cleared to ‘0’, the timer
starts counting ( in Figure 1.12.8).
When the timer X or Y stop control bit is set to ‘1’, the timer stops counting ( in Figure 1.12.8).
In the count operation, the contents of each timer are decremented by 1 at every rising edge of the
count source ( in Figure 1.12.8).
Reloading Timers
When a timer reaches ‘000016’ in the count operation, an underflow occurs at the subsequent rising
edge of the count source, and the contents of the timer latch are reloaded to the timer ( in Figure
1.12.8).
Timer Interrupt
At an underflow, the timer X or Y interrupt request bit is set to ‘1’; then a timer interrupt request is
generated ( in Figure 1.12.8).
event count mode