wm8940gefl-v Wolfson Microelectronics plc, wm8940gefl-v Datasheet - Page 61

• Manufacturer Part Number: wm8940gefl-v
• Description: Mono Codec With Speaker Driver
• Manufacturer: Wolfson Microelectronics plc

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Production Data
CONTROL INTERFACE
SELECTION OF CONTROL MODE AND 2-WIRE MODE ADDRESS
Table 53 Control Interface Mode Selection
USE OF MODE AS A GPIO PIN IN 3-WIRE MODE
Figure 33 Example Usage of MODE Pin to Generate a Clock out in 3-wire Mode
This example shows how the MODE_GPIO register bit interfaces to the MODE pad in the case
there MODE is used as a GPIO output. When MODE_GPIO is set, the internal version of
MODE is overridden to high and the MODE pin output driver is enabled. The pull up, which is
used to default 3-wire mode at start-up, is disabled as a power saving measure. MODE_GPIO
cannot be set in 2-wire m–de – this would prevent correct operation of the control interface.
Internal timing is arranged to ensure that the override is in place before the pull-up is disabled.
The control interface can operate as either a 3-wire or 2-wire interface. The MODE pin determines
the 2 or 3 wire mode as shown in Table 53.
The WM8940 is controlled by writing to registers through a serial control interface. A control word
consists of 24 bits. The first 7 bits (B23 to B16) are address bits that select which control register is
accessed. The remaining 16 bits (B15 to B0) are register bits, corresponding to the 16 bits in each
control register.
In 3-wire mode, MODE can be used as a GPIO pin. If MODE is being used as a GPIO output, the
partner device doesn’t have to drive MDE - the pin will be pulled-up internally causing 3-wire mode
will be selected. The GPIO function is enabled by setting the MODE_GPIO register bit. The MODE
pin can then be controlled using the GPIO register bits as described in Table 52.
To use MODE as a GPIO input, MODE must be undriven or driven high at start-up. Specifically
MODE must be high or hi-Z during an initial write to the control interface which sets the
MODE_GPIO register bit. After MODE_GPIO has been set, 3-wire mode selection is overridden
internally and the MODE pin can be used freely as a GPIO input or output.
MODE
High
Hi-Z
Low
INTERFACE FORMAT
2 wire
3 wire
3 wire
PD, Rev 4.2, April 2008
WM8940
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