Only For Training And Service Purposes - LG GT500 Service Manual

3. TECHNICAL DESCRIPTION
3.1.11 Bluetooth Interface
GT500 supports Bluetooth operation using ST's STLC2593C Bluetooth module.
A. General Description
The Bluetooth interface utilizes the SPI interface for control signals going to and from the Bluetooth module.
The SPI is also used for data transmissions.
It uses the PCM interface for transmitting audio to and from the Bluetooth module.
The Bluetooth module uses both the 26 MHz master clock signal and the 32,768 kHz low-frequency clock
signal for internal timing within the Bluetooth module. The intention is to use the low-frequency clock as a
low-power timing provider and to use the 26 MHz as a high precision timing reference used mainly by the
Bluetooth radio during operation.
The clock request mechanism is used to minimize current consumption for the total system.
The intention is to use the CLKREQ signal to ask for the master clock when needed, for example, when the
Bluetooth radio is operating.
B. SPI Interface
The physical SPI interface is made up of 5 signals : clock, chip select, data in, data out and interrupt. When the
SPI mode is selected , these signals are available through the BT_UART/BT_SPI and BT_HOST_WAKEUP pins.
The SPI interface is Master at the Host side, and Slave at the BT Controller side.
It is designed to work with the H4 and enhanced H4 protocol.
Also synchronous data packet transfer (sSCO) over HCI is supported.
The SPI data length and endianness are configurable.
The SPI interface can only operate in half duplex mode.
C. PCM Interface
The PCM interface is used to send audio to and from the Bluetooth module. The interface is a synchronous
interface using a PCM clock and a PCM sync signal for synchronization. Two data signals are used for data,
one in each direction.
The PCM clock signal operates at frequencies as high as 1 MHz. The word length of the audio data can be 8 or
16 bits. Furthermore, the PCM interface has a function known as MP-PCM, which is an addressing scheme,
used to have more than two devices talking on the bus.
To add this function, the data pins have to be bi-directional. Additionally, the position of the audio data
relative to the frame sync pulse must be selectable. During the periods within a frame that a device is not
transmitting audio data, it must put both PCM data signals in a high-impedance state to allow other devices
access.
D. Master Clock and Clock Request Interface
The master clock (MCLK) is a 26 MHz signal used as the high precision clock signal for the Bluetooth module.
The signal can be switched on and off by the platform. The master clock request (CLKREQ) is used by the
Bluetooth module to ask for the master clock.
If the Bluetooth module asserts the signal high, it gets the master clock. The other alternative for the
Bluetooth module is to set the clock request output to high impedance state, indicating that it does not
need the master clock. The Bluetooth module receives the master clock, if other parts of the chipset request
it.
E. Low Frequency Clock Interface
The low-frequency clock signal (RTCCLK) is used by the Bluetooth module as a low-power clock. The clock is
used in different Bluetooth modes, like sniff and park, to have a correct timing on the Bluetooth air interface
without having the master clock running.
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Only for training and service purposes