BM28723AMUV
14 Digital Sound Processing (DSP) - continued
14.12 Audio Output Level Meter
It is possible to output the peak level of the PCM data inputted into a PWM processor.
A peak value can be read using the 2-wire command interface as 16 bit data of an absolute value.
The interval holding a peak value can be selected from six steps (50ms step) from 50ms to 300ms.
A peak hold result can be selected from L channel, R channel, and a monaural channel {(Lch+Rch)/2}.
Audio Output Level Meter block diagram
I2S
DSP
Peak Hold
(Lch)
Peak Hold
(Rch)
0.5
Selector
0x75 METER_LOAD [1:0]
Level Output Register
0x76, 0x77 OUT_LEVEL [15:0]
Figure 62
Setting of the peak level hold time interval of Audio Output Level Meter
Default=0x00
Select Address
0x74[2:0]
Explanation of Operation
Hold time
50ms
Value
0x0
0x1
0x2
0x3
0x4
0x5
100ms
150ms
200ms
250ms
300ms
Specify the read-target signal of Audio Level Meter.
A value will be taken into a read-only register if a setting value is written in.
In order to update this register value, it is necessary to write in a setting value again.
Write only
Select Address
0x75[1:0]
Value
0x0
Explanation of Operation
The peak level of L channel
0x1
0x2
The peak level of R channel
The peak level of monaural channel {(Lch+Rch)/2}
Read-back of Audio Output Level
0x76 (upper 8 bits) and a 0x77 (lower 8 bits) commands are read for the maximum within the period appointed by the
command 0x74 using the 2-wire interface.
(Example)
When 0xFFFF is read, mean 1.0 (0dBFS).
When 0x8000 is read, mean 0.5 (-6dBFS).
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