TC9444F Datasheet, PDF (11/28 Pages) Toshiba Semiconductor – Single-Chip karaoke IC II

TC9444F
3.2 BOOT Command
One-byte command to initialize coefficient RAM.
Initializes coefficient RAM values to the internal BOOT ROM values, retaining the other command
interface settings.
After the BOOT command is received, initialization completes in a 1-fs cycle. Boot release is not
required.
When reset is made by setting the RESET pin to “L”, boot is still executed.
3.3 MUTE Command
One-byte command to clear data RAM and delay RAM, and to execute a soft mute using the digital
attenuator.
Table 3.2 MUTE Command
CH
3
1
0
CL
2
1
0
RAMCLR
0
MUTE
Note 5: At a reset, the initial value is CL = 0H.
MUTE: MUTE = “H” sets soft mute.
RAMCLR: RAMCLR = “H” clears data RAM and delay RAM.
At a soft mute, the time constant is determined by the operation sampling frequency and the time
constant selection bit set by the ATTA command. After the soft mute is released, the digital
attenuator is restored to the set level.
In data RAM, sequentially writing all-zero data (fixing the input data to 000000H) while RAMCLR
= “H” clears data RAM. Therefore, the number of fs cycles required to completely clear data RAM
depends on the program. Normally, several cycles are required.
For a program which is written to in one place only, a 128-word update takes no more than 3 ms.
In delay RAM, after RAMCLR = H, 0000H is sequentially written to delay RAM at subsequent
write operations (INIT operation).
When using delay RAM to significantly change the effect of the SFC processing, to clear the data in
RAM, take the following steps. First set the MUTE bit. Then, after waiting only the length of the
digital attenuator time constant, set RAMCLR to “H” to clear the data in RAM. Then set the
RAMCLR and MUTE bits to “L”. This will enable you to change the signal processing content without
any switching noise.
3.4 KEYCON Command
One-byte command to control the amount of key shift. The CL value indicates the amount of key
shift.
The difference between the 20H command and the 28H command is the point at which key control
processing completely stops. Using the 20H command to turn key control off disables the use of
internal delay RAM in the key control processing, thus allowing delay RAM to be allocated to other
processing.
The amount of key shift set by the KEYCON command applies to both L and R stereo key control
and to monaural key control. The key shift is set in semitone steps.
As delay RAM is used in key control processing, when switching the key shift setting between 0 and
a value other than 0, the signal is intermittent. The soft mute automatically comes on to avoid
switching noise at this time. After the command is issued, the following steps are performed
automatically.
Mute ® Internal settings switched ® Mute released
This series of processing operations takes around 46 ms to execute.
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2002-01-11