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BTM521 DATASHEET

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5.6

Serial Interfaces

5.6.1

UART

This is a standard UART interface for communicating with other serial devices. The UART

interface provides a simple mechanism for communicating with other serial devices using

the RS232 protocol.

When the module is connected to another digital device, UART_RX and UART_TX

transfer data between the two devices. The remaining two signals, UART_CTS and

UART_RTS, can be used to implement RS232 hardware flow control where both are

active low indicators.

Note: The serial port interface(UART)can be used for system debugging. Don’t

support to use command set for profile function application by UART, such as

HFP/A2DP/AVRCP and so on. These profiles function application can be controlled

only by PIO, such as pairing/connect/answer/play/pause/next/previous function

application and so on.

5.6.2

SPI

The synchronous serial port interface (SPI) can be used for system debugging. It can also be

used for in-system programming for the flash memory within the module. SPI interface

uses the SPI_MOSI, SPI_MISO, SPI_CSB and SPI_CLK pins. Testing points for the SPI

interface are reserved on board in case that the firmware shall be updated during

manufacture.

The module operates as a slave and thus SPI_MISO is an output of the module.

SPI_MISO is not in high-impedance state when SPI_CSB is pulled high. Instead, the

module outputs 0 if the processor is running and 1 if it is stopped. Thus the module

should NOT be connected in

a multi-slave arrangement by simple parallel connection

of slave SPI_MISO lines.

Figure 7