PC912XDP512F0MPVR datasheet(520/1348 Pages) FREESCALE

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Chapter 12 Serial Peripheral Interface (S12SPIV4)

MC9S12XDP512 Data Sheet, Rev. 2.21

520

Freescale Semiconductor

12.3.2.1

SPI Control Register 1 (SPICR1)

Read: Anytime

Write: Anytime

76543210

SPIE

SPE

SPTIE

MSTR

CPOL

CPHA

SSOE

LSBFE

Reset

00000100

Figure 12-3. SPI Control Register 1 (SPICR1)

Table 12-1. SPICR1 Field Descriptions

Field

Description

SPIE

SPI Interrupt Enable Bit — This bit enables SPI interrupt requests, if SPIF or MODF status ﬂag is set.

0 SPI interrupts disabled.

1 SPI interrupts enabled.

SPE

SPI System Enable Bit — This bit enables the SPI system and dedicates the SPI port pins to SPI system

functions. If SPE is cleared, SPI is disabled and forced into idle state, status bits in SPISR register are reset.

0 SPI disabled (lower power consumption).

1 SPI enabled, port pins are dedicated to SPI functions.

SPTIE

SPI Transmit Interrupt Enable — This bit enables SPI interrupt requests, if SPTEF ﬂag is set.

0 SPTEF interrupt disabled.

1 SPTEF interrupt enabled.

MSTR

SPI Master/Slave Mode Select Bit — This bit selects whether the SPI operates in master or slave mode.

Switching the SPI from master to slave or vice versa forces the SPI system into idle state.

0 SPI is in slave mode.

1 SPI is in master mode.

CPOL

SPI Clock Polarity Bit — This bit selects an inverted or non-inverted SPI clock. To transmit data between SPI

modules, the SPI modules must have identical CPOL values. In master mode, a change of this bit will abort a

transmission in progress and force the SPI system into idle state.

0 Active-high clocks selected. In idle state SCK is low.

1 Active-low clocks selected. In idle state SCK is high.

CPHA

SPI Clock Phase Bit — This bit is used to select the SPI clock format. In master mode, a change of this bit will

abort a transmission in progress and force the SPI system into idle state.

0 Sampling of data occurs at odd edges (1,3,5,...,15) of the SCK clock.

1 Sampling of data occurs at even edges (2,4,6,...,16) of the SCK clock.

SSOE

Slave Select Output Enable — The SS output feature is enabled only in master mode, if MODFEN is set, by

asserting the SSOE as shown in Table 12-2. In master mode, a change of this bit will abort a transmission in

progress and force the SPI system into idle state.

LSBFE

LSB-First Enable — This bit does not affect the position of the MSB and LSB in the data register. Reads and

writes of the data register always have the MSB in bit 7. In master mode, a change of this bit will abort a

transmission in progress and force the SPI system into idle state.

0 Data is transferred most signiﬁcant bit ﬁrst.

1 Data is transferred least signiﬁcant bit ﬁrst.

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