7480 datasheet(82/337 Pages) RENESAS

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1.12 Timer X and Timer Y

HARDWARE

7480 Group and 7481 Group User's Manual

Count Operation

The count operation (start/stop) of timer X or timer Y is controlled by the timer X or Y stop control bit of

the timer XY control register as follows:

• When the timer X or Y stop control bit is set to ‘0’, the timer starts counting.

• 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.

The timer X or Y stop control bit is recognized during the HIGH time of the count source. When the count

has stopped, the count source cannot be accepted.

In the PWM mode, the high- and the low-order bytes of timer X or Y counts down each as an 8-bit timer.

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 the pulse period measurement mode or the pulse width measurement mode, when a timer reaches

‘000016’, an underflow occurs and a timer wraps around to ‘FFFF16’ at the subsequent rising edge of the

count source.

In the PWM mode, the high- and the low-order byte of a timer count down each as an 8-bit timer. When

either the high- or the low-order byte of the timer becomes ‘0116’, an underflow occurs at the subsequent

rising edge of the count source, and the contents of the timer latch are reloaded to the timer.

Timer Interrupt

At an underflow, the timer X or Y interrupt request bit of interrupt request register 1 is set to ‘1’; then a

timer interrupt request is generated.

Table 1.12.1 lists the relation between timer count periods and values set to timer X and timer Y.

Table 1.12.1 Relation between Timer Count Periods and Values Set to Timer X and Timer Y

Clock Input

Oscillation Frequency

Count Source

(Cycle Time)

f(XIN) = 8 MHz

f(XIN) = 4 MHz

f(XIN)/2

(0.25

µs)

f(XIN)/8

µs)

f(XIN)/16

µs)

f(XIN)/2

(0.5

µs)

f(XIN)/8

µs)

f(XIN)/16

µs)

High-

order

0116

0316

0916

1316

6116

C316

Low-

order

F316

E716

C316

8716

A716

4F16

Low-

order

E716

CF16

8716

0F16

4F16

High-

order

0316

0716

1316

2716

C316

Low-

order

9F16

3F16

1F16

3F16

High-

order

0F16

1F16

4E16

9C16

High-

order

0716

0F16

2716

4E16

Low-

order

CF16

9F16

0F16

1F16

High-

order

0116

0316

0916

1316

6116

C316

Low-

order

F316

E716

C316

8716

A716

4F16

High-

order

0016

0116

0416

0916

3016

6116

Low-

order

F916

F316

E116

C316

D316

A716

–

1 ms

2 ms

5 ms

10 ms

50 ms

100 ms

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