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7480 Group and 7481 Group User's Manual

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1.12 Timer X and Timer Y

HARDWARE

1.12.9 Programmable One-Shot Output Mode

(1)

Operations in Programmable One-Shot Output Mode

Operations in the programmable one-shot output mode is explained with Figure 1.12.21.

Count Sources

In the programmable one-shot output 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

• f(XIN)/16

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 1.12.21).

• 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 is cleared to ‘0’, the timer starts counting ( in Figure

1.12.21).

• When the timer X or Y stop control bit is set to ‘1’, the timer stops counting.

In the count operation, the contents of each timer are decremented by 1 at every rising edge of the

count source ( in Figure 1.12.21).

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

1.12.21).

When the valid edge of an INT pin input is detected, the contents of the timer latch are also reloaded

( in Figure 1.12.21).

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 1.12.21).

Generation of Programmable One-Shot Pulse

• When timer X is used, a one-shot pulse is output from the CNTR0 pin when the valid edge of an

INT0 pin input is detected ( in Figure 1.12.21).

• When timer Y is used, a one-shot pulse is output from the CNTR1 pin when the valid edge of an

INT1 pin input is detected.

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