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4.6

Serial Interfaces

4.6.1

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.

4.6.2

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