PXD10RM Datasheet, PDF (309/1332 Pages) Freescale Semiconductor, Inc – PXD10 Microcontroller

11.8.2 Start and Stop of DSPI Transfers
The DSPI has two operating states: STOPPED and RUNNING. The states are independent of DSPI
configuration. The default state of the DSPI is STOPPED. In the STOPPED state no serial transfers are
initiated in master mode and no transfers are responded to in slave mode. The STOPPED state is also a
safe state for writing the various configuration registers of the DSPI without causing undetermined results.
The TXRXS bit in the DSPIx_SR is cleared in this state. In the RUNNING state, serial transfers take place.
The TXRXS bit in the DSPIx_SR is set in the RUNNING state.
Figure 11-12 shows a state diagram of the start and stop mechanism.
RESET
Power-on-Reset 0
1
STOPPED
TXRXS = 0
RUNNING
TXRXS = 1
2
Figure 11-12. DSPI Start and Stop State Diagram
The transitions are described in Table 11-18.
Table 11-18. State Transitions for Start and Stop of DSPI Transfers
Transition # Current State Next State
Description
0
RESET
STOPPED Generic power-on-reset transition
1
STOPPED RUNNING The DSPI starts (transitions from STOPPED to RUNNING) when all
of the following conditions are true:
• EOQF bit is clear
• Debug mode is unselected or the FRZ bit is clear
• HALT bit is clear
2
RUNNING STOPPED The DSPI stops (transitions from RUNNING to STOPPED) after the
current frame for any one of the following conditions:
• EOQF bit is set
• Debug mode is selected and the FRZ bit is set
• HALT bit is set
State transitions from RUNNING to STOPPED occur on the next frame boundary if a transfer is in
progress, or on the next system clock cycle if no transfers are in progress.
11.8.3 Serial Peripheral Interface (SPI) Configuration
The SPI configuration transfers data serially using a shift register and a selection of programmable transfer
attributes. The DSPI is in SPI configuration when the DCONF field in the DSPIx_MCR is 0b00. The SPI
frames can be from 4 to 16 bits long. The data to be transmitted can come from queues stored in RAM
external to the DSPI. Host software or an eDMA controller can transfer the SPI data from the queues to a
Freescale Semiconductor
PXD10 Microcontroller Reference Manual, Rev. 1
Preliminary—Subject to Change Without Notice
11-27