C8051F2XX Datasheet, PDF (111/146 Pages) Silicon Laboratories – Mixed Signal 8 kB ISP Flash MCU Family

C8051F2xx
NSS
Slave
Device
NSS
Slave
Device
NSS
Slave
Device
VDD
Master
Device
MISO
MOSI
SCK
Figure 15.2. SPI Block Diagram
15.1. Signal Descriptions
The four signals used by the SPI (MOSI, MISO, SCK, NSS) are described below.
15.1.1. Master Out, Slave In
The master-out, slave-in (MOSI) signal is an output from a master device and an input to slave devices. It
is used to serially transfer data from the master to the slave. Data is transferred most-significant bit first.
15.1.2. Master In, Slave Out
The master-in, slave-out (MISO) signal is an output from a slave device and an input to the master device.
It is used to serially transfer data from the slave to the master. Data is transferred most-significant bit first.
A SPI slave places the MISO pin in a high-impedance state when the slave is not selected.
15.1.3. Serial Clock
The serial clock (SCK) signal is an output from the master device and an input to slave devices. It is used
to synchronize the transfer of data between the master and slave on the MOSI and MISO lines.
15.1.4. Slave Select
The slave select (NSS) signal is an input used to select the SPI module when in slave mode by a master,
or to disable the SPI module when in master mode. When in slave mode, it is pulled low to initiate a data
transfer and remains low for the duration of the transfer.
Rev. 1.6
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