AK4637EN Datasheet, PDF (35/96 Pages) Asahi Kasei Microsystems – 24bit Mono CODEC with MIC/SPK-AMP

[AK4637]
■ Audio Interface Format
Four types of data formats are available and can be selected by setting the DIF1-0 bits (Table 19). In all
modes, the serial data is MSB first, 2’s complement format. Audio interface formats can be used in both
master and slave modes. FCK and BICK are output from the AK4637 in master mode, but must be input
to the AK4637 in slave mode.
Mode
DIF1
bit
0
0
1
0
2
1
3
1
DIF0
bit
0
1
0
1
SDTO (ADC)
SDTI (DAC)
BICK
16bit DSP Mode 16bit DSP Mode
 16fs
24/16bit
MSB justified
16bit LSB justified
 32fs
24bit MSB justified 24bit MSB justified  48fs
24/16 bit
I²S Compatible
24/16 bit
I²S Compatible
=32fs or
 48fs
Table 19. Audio Interface Format
Figure
Table 20
Figure 31
Figure 32 (default)
Figure 33
If 24-bit(or 16-bit) data that ADC outputs is converted to 8-bit data by removing LSB 16-bit(8-bit), “-1” at
24bit(16bit) data is converted to “-1” at 8-bit data. And when the DAC playbacks this 8-bit data, “-1” at 8-bit
data will be converted to “-65536” at 24-bit (“-256” at 16-bit) data which is a large offset. This offset can be
removed by adding the offset of “32768” at 24-bit (“128” at 16bit) to 24-bit(16-bit) data before converting
to 8-bit data.
In Mode 1, 2 and 3, the SDTO is clocked out on the falling edge (“↓”) of BICK and the SDTI is latched on
the rising edge (“↑”).
In Mode 0 (16bit DSP mode), the audio I/F timing is changed by BCKP and MSBS bits (Table 20).
DIF1
bit
0
DIF0
bit
0
MSBS
bit
0
0
1
1
BCKP
bit
Audio Interface Format
Figure
MSB of SDTO is output by the rising edge (“”) of
the first BICK after the rising edge (“”) of FCK.
0 MSB of SDTI is latched by the falling edge (“”) of Figure 27 (default)
the BICK just after the output timing of SDTO’s
MSB.
MSB of SDTO is output by the falling edge (“”) of
the first BICK after the rising edge (“”) of FCK.
1 MSB of SDTI is latched by the rising edge (“”) of Figure 28
the BICK just after the output timing of SDTO’s
MSB.
MSB of SDTO is output by next rising edge (“”) of
the falling edge (“”) of the first BICK after the
0
rising edge (“”) of FCK.
MSB of SDTI is latched by the falling edge (“”) of
Figure 29
the BICK just after the output timing of SDTO’s
MSB.
MSB of SDTO is output by next falling edge (“”)
of the rising edge (“”) of the first BICK after the
1
rising edge (“”) of FCK.
MSB of SDTI is latched by the rising edge (“”) of
Figure 30
the BICK just after the output timing of SDTO’s
MSB.
Table 20. Audio Interface Format in Mode 0
015010680-E-00
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2015/09