µPD61P24

8

10. TIMER

The timer block determines the transmission output pattern. The timer consists of 10 bits, of which 9 bits serve

as the 9-bit down counter and the remaining 1 bit serves as the 1-bit latch, which determines the carrier output

validity.

starting down count operation. Down counting stops after all of the 9 bits become 0. When down counting is stopped,

the signal indicating that the timer operation has stopped, is output. If the CPU is at standby (HALT TIMER) for

the timer operation completion, the standby (HALT) condition is released and the next instruction will be executed.

If the next instruction again sets the value of the down counter, down counting continues without any error (the carrier

output of the REM pin is not affected).

Set the down count time according to the following calculation; (set value (HEX) + 1)

to the timer is done by the timer manipulation instruction.

When the down counter is operating, the remote control transmission carrier can be output to the REM pin.

Whether or not to output the carrier can be selected by the MSB for the timer register block. Set “1”, when outputting

the carrier, or “0”, when not outputting the carrier.

If all the down counter bits become “0”, when outputting the carrier, the carrier output will be stopped. When

not outputting the carrier, the REM pin output will become low level.

A signal in synchronization with the REM output is output to the S-OUT pin. However, the waveform for the S-

OUT pin is low, when the carrier is being output to the REM pin, or it is high, when the carrier is not being output

to the REM pin.

If the HALT instruction, which initiates the oscillation stop mode, is executed when the down counter is operating,

the oscillation stop mode is initiated after down counting is stopped (after 0).

At reset (all clear) time, the REM pin goes low and S-OUT pin goes high. All 10 bits of the timer are cleared to

000H.

Caution Because the timer clock is not synchronized with the carrier output, the pulse width may be

shortened at the beginning and end of the carrier output.

Figure 10-1. Timer Block Organization

S-OUT

REM

Carrier

(fosc/12, fosc/8)

Selected by control register

Clear

Set by timer mainpulation instruction

9-bit down counter

Zero detection circuit

D of control register P

(Timer RUN/STOP)

21

1/0

MSB

fosc/8