Table of Contents
Advertisement
Therefore, when the LSI moves from operating mode to
standby mode, popcorn noise may be generated by the
sudden changes in the output of the O/A converter. To
prevent this, the output of the O/A converter is grad-
ually reduced prior to entering the standby mode (see
Fig. 3-5).
Also, when changing from standby to operating mode, the
O/A output is gradually raised to AC 0 from the time when
clock oscillation starts and completes in response to the
standby release signal generated by input of the CS and
ST
signals (see Fig. 3-6).
The transition time for the O/A output is approximately
46.5ms and which enough to suppress this type of noise.
O/A converter input
lFFH
AVO
10011
OOOH~----------------------------------~-----------
O/A output
operating model
I
transition time
standby mode
Start standby operation
Fig. 3-5
O/A Converter Output when Entering Standby Mode
O/A converter input
lFFH
AVO
100H
OOOH~------------------------~-------------------------------
Clock oscilla
Standby mOdel tion time
I
Standby release signal
O/A output
transition time
(start speech synthesis signal)
loperatin g mod
Fig. 3-6
O/A Converter Output when Releasing Standby Mode
3-7
Advertisement
Table of Contents
