NEC PD78F9488 - Manual (Page 287)

CHAPTER 15 REMOTE CONTROLLER RECEIVER ( µ PD789489, 78F9489 ONLY)
User’s Manual U15331EJ4V1UD
287
15.4.6 Noise elimination
This remote controller receiver provides a function that supplies the signals input from the outside to the RIN pin
after eliminating noise.
Noise width can be eliminated by setting bit 5 (PRSEN) and bit 6 (NCW) of the remote controller receive control
register (RMCN) as shown in Figure 15-2.
Table 15-2. Noise Elimination Width
PRSEN Division
Control Signal
NCW Noise Elimination Width Control
Signal
Internal Operation Clock Cycle After
Division Control by PRSEN (1/f
PRS
)
Eliminatable Noise
Width
0 0 1/f
REM
Less than 1/f
REM
0 1 1/f
REM
Less than 2/f
REM
1 0 2/f
REM
Less than 2/f
REM
1 1 2/f
REM
Less than 4/f
REM
Remark f
REM
: Source clock of remote controller counter
A noise elimination operation is performed by using the internal operation clock after division control by PRSEN.
Then, after the external input signal from RIN pin has been synchronized with the clock,
If NCW = 0, the signal after sampling is performed twice is processed as a RIN input in the circuit.
If NCW = 1, the signal after sampling is performed three times is processed as a RIN input in the circuit.
The following shows the flow of a noise elimination operation.
<1> Select whether or not the internal operation clock is divided by PRSEN.
PRSEN = 0: Not divided (f
PRS
= f
REM
)
PRSEN = 1: Divided (f
PRS
= f
REM
/2)
<2> Synchronize the external input signal from the RIN pin with the internal operation clock.
<3> Generate a signal (samp1) sampling the synchronized signal for the first time.
(The signal is later than the synchronized signal by one clock.)
<4> Generate a signal (samp2) sampling the synchronized signal and samp1 for the second time.
(When synchronized signal = samp1 = H, samp1 is latched.)
<5> Generate a signal (samp3) sampling the synchronized signal and samp2 for the third time.
(When synchronized signal = samp2 = H, samp2 is latched.)
<6> Select a signal to be the RIN input in the circuit using NCW.
NCW = 0: samp2 is processed as the RIN input in the circuit.
NCW = 1: samp3 is processed as the RIN input in the circuit.
Figure 15-8 shows an example of a noise elimination operation.