DSP56857 datasheet(299/662 Pages) FREESCALE

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Interrupts

Serial Peripheral Interface (SPI), Rev. 4

Freescale Semiconductor

11-29

The following items are reset only by a system reset:

•

The SPDTR and SPDRR Registers

•

All control bits in the SPSCR Register (MODFEN, ERRIE, SPR1, and SPR0)

•

The status flags SPRF, OVRF, and MODF

By not resetting the control bits when SPE is low, it is possible to clear SPE between

transmissions without having to set all control bits again when SPE is set back high for the next

transmission.

By not resetting the SPRF, OVRF, and MODF flags, it is possible to service the interrupts after

the SPI has been disabled. Disable SPI by writing 0 to the SPE bit. SPI can also be disabled by a

Mode Fault occurring in a SPI configured as a Master with MODF.

11.13 Interrupts

Four SPI status flags can be enabled to generate interrupt requests.

The following sources in the SPI Status and Control Register can generate interrupt requests:

•

The SPI Transmitter Interrupt Enable (SPTIE) bit enables the SPTE flag to generate

transmitter interrupt requests provided the SPI is enabled (SPE = 1). The clearing

mechanism for the SPTE flag is always just a write to the Data Transmit register.

•

The SPI Receiver Interrupt Enable (SPRIE) bit enables the SPRF bit to generate receiver

interrupt requests regardless of the state of the SPE bit. The clearing mechanism for the

SPRF flag is always just a read to the Data Receive register.

•

The Error Interrupt Enable (ERRIE) bit enables both the MODF and OVRF bits to

generate a receiver/error interrupt request.

•

The Mode Fault Enable (MODFEN) bit can prevent the MODF flag from being set so only

the OVRF bit is enabled by the ERRIE bit to generate receiver/error interrupt requests.

Table 11-6. SPI Interrupts

Flag

Request

SPTE (Transmitter Empty)

SPI Transmitter Interrupt Request (SPTIE = 1,SPE = 1)

SPRF (Receiver Full)

SPI Receiver Interrupt Request (SPRIE = 1)

OVRF (Overflow)

SPI Receiver/Error Interrupt Request (ERRIE = 1)

MODF (Mode Fault)

SPI Receiver/Error Interrupt Request (ERRIE = 1)

DSP56857 Datasheet(PDF) 299 Page - Freescale Semiconductor, Inc

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