STM8S datasheet(263/467 Pages) STMICROELECTRONICS

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RM0016

Serial peripheral interface (SPI)

287

20.3

SPI functional description

20.3.1

SPI general description

The block diagram of the SPI is shown in Figure 91.

Figure 91. SPI block diagram

The SPI is connected to external devices through four pins:

•

MISO: Master In / Slave Out data (port C7). This pin can be used to transmit data in

slave mode and receive data in master mode.

•

MOSI: Master Out / Slave In data (port C6). This pin can be used to transmit data in

master mode and receive data in slave mode.

•

SCK: Serial Clock output (port C5) for SPI masters and Serial Clock input for SPI

slaves.

•

NSS: Slave select (port E5). This is a optional pin to select a slave device. This pin acts

as a ‘chip select’ to let the SPI master communicate with slaves individually and to

avoid contention on the data lines. Slave NSS inputs can be driven by standard I/O

ports on the master device. When configured in master mode (MSTR bit =1) and if NSS

is pulled low, the SPI enters master mode fault state: the MSTR bit is automatically

reset and the device is configured in slave mode (refer to Section 20.3.9: Error flags on

page 279).

A basic example of interconnections between a single master and a single slave is

illustrated in Figure 92.

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