MPC555CME Freescale Semiconductor, MPC555CME Datasheet - Page 500

• Manufacturer Part Number: MPC555CME
• Description: KIT EVALUATION FOR MPC555
• Manufacturer: Freescale Semiconductor
• Type: Microcontrollerr

Specifications of MPC555CME

• Contents: Module Board, Installation Guide, Power Supply, Cable, Software and more
• Processor To Be Evaluated: MPC555
• Data Bus Width: 32 bit
• Interface Type: RS-232
• For Use With/related Products: MPC555
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

MPC555
USER’S MANUAL
After pins are assigned and configured, write data to be transmitted into transmit RAM.
Command RAM is not used in slave mode, and does not need to be initialized. Set the
queue pointers, as appropriate.
When SPE is set and MSTR is clear, a low state on the slave select PCS[0]/SS pin
begins slave mode operation at the address indicated by NEWQP. Data that is re-
ceived is stored at the pointer address in receive RAM. Data is simultaneously loaded
into the data serializer from the pointer address in transmit RAM and transmitted.
Transfer is synchronized with the externally generated SCK. The CPHA and CPOL
bits determine upon which SCK edge to latch incoming data from the MISO pin and to
drive outgoing data from the MOSI pin.
Because the command RAM is not used in slave mode, the CONT, BITSE, DT, DSCK,
and peripheral chip-select bits have no effect. The PCS[0]/SS pin is used only as an
input.
The SPBR, DT and DSCKL fields in SPCR0 and SPCR1 bits are not used in slave
mode. The QSPI drives neither the clock nor the chip-select pins and thus cannot con-
trol clock rate or transfer delay.
Because the BITSE option is not available in slave mode, the BITS field in SPCR0
specifies the number of bits to be transferred for all transfers in the queue. When the
number of bits designated by BITS[3:0] has been transferred, the QSPI stores the
working queue pointer value in CPTQP, increments the working queue pointer, and
loads new transmit data from transmit RAM into the data serializer. The working queue
pointer address is used the next time PCS[0]/SS is asserted, unless the RCPU writes
to NEWQP first.
The QSPI shifts one bit for each pulse of SCK until the slave select input goes high. If
SS goes high before the number of bits specified by the BITS field is transferred, the
QSPI resumes operation at the same pointer address the next time SS is asserted.
The maximum value that the BITS field can have is 16. If more than 16 bits are trans-
mitted before SS is negated, pointers are incremented and operation continues.
The QSPI transmits as many bits as it receives at each queue address, until the BITS
value is reached or SS is negated. SS does not need to go high between transfers as
the QSPI transfers data until reaching the end of the queue, whether SS remains low
or is toggled between transfers.
When the QSPI reaches the end of the queue, it sets the SPIF flag. If the SPIFIE bit
in SPCR2 is set, an interrupt request is generated when SPIF is asserted. At this point,
the QSPI clears SPE and stops unless wraparound mode is enabled.
Slave wraparound mode is enabled by setting the WREN bit in SPCR2. The queue can
wrap to pointer address 0x0 or to the address pointed to by NEWQP, depending on
the state of the WRTO bit in SPCR2. Slave wraparound operation is identical to master
wraparound operation.
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MPC556
QUEUED SERIAL MULTI-CHANNEL MODULE
Rev. 15 October 2000
MOTOROLA
14-38