wm8941 Wolfson Microelectronics plc, wm8941 Datasheet - Page 65
![no-image](/images/no-image-200.jpg)
wm8941
Manufacturer Part Number
wm8941
Description
Mono Codec With Speaker Driver And Video Buffer
Manufacturer
Wolfson Microelectronics plc
Datasheet
1.WM8941.pdf
(94 pages)
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Company:
Part Number:
wm8941G
Manufacturer:
MITSUMI
Quantity:
971
Part Number:
wm8941GEFL
Manufacturer:
WOLFSON
Quantity:
20 000
Production Data
w
COMPANDING
Table 51 Companding Control
The WM8941 supports A-law and μ-law companding on both transmit (ADC) and receive (DAC)
sides. Companding can be enabled on the DAC or ADC audio interfaces by writing the appropriate
value to the DAC_COMP or ADC_COMP register bits respectively. If packed mode companding is
desired the WL8 register bit is available. It will override the normal audio interface WL bits to give an
8-bit word length. Refer to Table 44 Audio Interface Control for setting the output word length.
Companding involves using a piecewise linear approximation of the following equations (as set out
by ITU-T G.711 standard) for data compression:
μ-law (where μ=255 for the U.S. and Japan):
F(x) = ln( 1 + μ|x|) / ln( 1 + μ)
A-law (where A=87.6 for Europe):
F(x) = A|x| / ( 1 + lnA) } for x ≤ 1/A
F(x) = ( 1 + lnA|x|) / (1 + lnA) } for 1/A ≤ x ≤ 1
The companded data is also inverted as recommended by the G.711 standard (all 8 bits are inverted
for μ-law, all even data bits are inverted for A-law). The data will be transmitted as the first 8 MSB’s
of data.
R5
Companding
control
REGISTER
ADDRESS
6
4:3
2:1
0
BIT
DAC_LOOPBACK 0
DAC_COMP
ADC_COMP
ADC_LOOPBACK 0
LABEL
-1 ≤ x ≤ 1
0
0
DEFAULT
Digital loopback function
0=No DAC loopback
1=Loopback enabled, DAC audio interface
output is fed directly into ADC audio
interface input.
DAC decompanding
00=off
01=reserved
10=µ-law
11=A-law
ADC companding
00=off
01=reserved
10=µ-law
11=A-law
Digital loopback function
0=No ADC loopback
1=Loopback enabled, ADC data output is
fed directly into DAC data input.
DESCRIPTION
PD, Rev 4.0, August 2008
WM8941
65