LG KT520 Service Manual page 35

3. TECHNICAL BRIEF
3.1.10 Bluetooth Interface
KT520 supports Bluetooth operation using ST's STLC2500C 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 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 protocol. It does not support HCI synchronous data packet transfer.
Data are transferred on the SPI interface in byte format, LSB first.
The SPI interface can operate only 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.
LGE Internal Use Only Copyright © 2008 LG Electronics. Inc. All right reserved.
- 36 -
Only for training and service purposes