WM8976 Wolfson Microelectronics Ltd., WM8976 Datasheet - Page 73

• Manufacturer Part Number: WM8976
• Description: The WM8976 is a low power, high quality stereo codec designed for portable applications such as Digital still camera or Digital Camcorde
• Manufacturer: Wolfson Microelectronics Ltd.

Pre-Production
OUTPUT SWITCHING (JACK DETECT)
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Table 61 CSB/GPIO Control
Note: If MODE is set to 3 wire mode, CSB/GPIO1 shall be used as CSB input irrespective of the
GPIO1SEL[2:] bits.
Note that SLOWCLKEN must be enabled when using the Jack Detect function.
For further details of the Jack detect operation see the OUTPUT SWITCHING section.
When the device is operated using a 2-wire interface the CSB/GPIO1 pin can be used as a switch
control input to automatically disable one set of outputs and enable another the most common use
for this functionality is as jack detect circuitry. The L2/GPIO2 and R2/GPIO3 pins can also be used
for this purpose.
The GPIO pins have an internal de-bounce circuit when in this mode in order to prevent the output
enables from toggling multiple times due to input glitches. This de-bounce circuit is clocked from a
slow clock with period 2
Notes:
1.
2.
Switching on/off of the outputs is fully configurable by the user. Each output, OUT1, OUT2, OUT3
and OUT4 has 2 associated enables. OUT1_EN_0, OUT2_EN_0, OUT3_EN_0 and OUT4_EN_0
are the output enable signals which are used if the selected jack detection pin is at logic 0 (after de-
bounce). OUT1_EN_1, OUT2_EN_1, OUT3_EN_1 and OUT4_EN_1 are the output enable signals
which are used if the selected jack detection pin is at logic 1 (after de-bounce).
The jack detection enables operate as follows:
All OUT_EN signals have an AND function performed with their normal enable signals (in Table 49).
When an output is normally enabled as per Table 49 the selected jack detection enable (controlled
by selected jack detection pin polarity) is set 0; it will turn the output off. If the normal enable signal is
already OFF (0), the jack detection signal will have no effect due to the AND function.
During jack detection if the user desires an output to be un-changed whether the jack is in or not,
both the JD_EN settings i.e. JD_EN0 and JD_EN1, should be set to 0000.
R8
GPIO
Control
REGISTER
ADDRESS
The SLOWCLKEN bit must be enabled for the jack detect circuitry to operate.
The GPIOPOL bit is not relevant for jack detection, it is the signal detected at the pin which is
used
2:0
3
5:4
BIT
21
x MCLK and is enabled by the SLOWCLKEN bit.
GPIO1SEL
GPIO1POL
OPCLKDIV
LABEL
000
0
00
DEFAULT
CSB/GPIO1 pin function select:
000= input (CSB/jack detection:
depending on MODE setting)
001= reserved
010=Temp ok
011=Amute active
100=PLL clk o/p
101=PLL lock
110=logic 0
111=logic 1
GPIO1 Polarity invert
0=Non inverted
1=Inverted
PLL Output clock division ratio
00=divide by 1
01=divide by 2
10=divide by 3
11=divide by 4
DESCRIPTION
PP Rev 3.0 April 2006
WM8976
73