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MC9S12VR-Family - Data Sheet - Freescale Semiconductor

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Receive Shift Register<br />

SPIF<br />

SPI <strong>Data</strong> Register<br />

Receive Shift Register<br />

SPIF<br />

SPI <strong>Data</strong> Register<br />

11.4 Functional Description<br />

<strong>Data</strong> A Received <strong>Data</strong> B Received<br />

<strong>Data</strong> A <strong>Data</strong> B<br />

<strong>Data</strong> A<br />

= Unspecified = Reception in progress<br />

Figure 11-9. Reception with SPIF serviced in Time<br />

<strong>Data</strong> A Received <strong>Data</strong> B Received<br />

<strong>Data</strong> A <strong>Data</strong> B<br />

<strong>Data</strong> A<br />

= Unspecified = Reception in progress<br />

Figure 11-10. Reception with SPIF serviced too late<br />

<strong>MC9S12VR</strong> <strong>Family</strong> Reference Manual, Rev. 2.8<br />

Serial Peripheral Interface (S12SPIV5)<br />

SPIF Serviced<br />

<strong>Data</strong> B<br />

<strong>Data</strong> C Received<br />

<strong>Data</strong> C<br />

<strong>Data</strong> C<br />

<strong>Data</strong> C Received<br />

<strong>Data</strong> B Lost<br />

SPIF Serviced<br />

<strong>Data</strong> C<br />

<strong>Data</strong> C<br />

The SPI module allows a duplex, synchronous, serial communication between the MCU and peripheral<br />

devices. Software can poll the SPI status flags or SPI operation can be interrupt driven.<br />

The SPI system is enabled by setting the SPI enable (SPE) bit in SPI control register 1. While SPE is set,<br />

the four associated SPI port pins are dedicated to the SPI function as:<br />

• Slave select (SS)<br />

• Serial clock (SCK)<br />

• Master out/slave in (MOSI)<br />

• Master in/slave out (MISO)<br />

<strong>Freescale</strong> <strong>Semiconductor</strong> 355

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