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Generally, more than one slave device can be connected to the module master. Six
Peripheral Chip Select (PCS) signals of the module masters can be used to select which
of the slaves to communicate with. Refer to the chip configuration chapter for the number
of PCS signals used in this MCU.
The SPI configuration share transfer protocol and timing properties which are described
independently of the configuration in Transfer formats . The transfer rate and delay
settings are described in Module baud rate and clock delay generation.
46.4.1 Start and Stop of module transfers
The module has two operating states: Stopped and Running. Both the states are
independent of it's configuration. The default state of the module 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 module without causing undetermined results. In the
Running state serial transfers take place.
The TXRXS bit in the SR indicates the state of module. The bit is set if the module is in
Running state.
The module starts or transitions to Running when all of the following conditions are true:
• SR[EOQF] bit is clear
• MCU is not in the Debug mode or the MCR[FRZ] bit is clear
• MCR[HALT] bit is clear
The module stops or transitions from Running to Stopped after the current frame when
any one of the following conditions exist:
• SR[EOQF] bit is set
• MCU in the Debug mode and the MCR[FRZ] bit is set
• MCR[HALT] bit is set
State transitions from Running to Stopped occur on the next frame boundary if a transfer
is in progress, or immediately if no transfers are in progress.
Functional description
K20 Sub-Family Reference Manual, Rev. 1.1, Dec 2012
1210
Preliminary
Freescale Semiconductor, Inc.
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