Motorola MPC533 Reference Manual page 632

Queued Serial Peripheral Interface
Pin Names
Master in slave out
Master out slave in
Serial clock
Peripheral chip selects
2
Peripheral chip select
3
Slave select
4
Slave select
1
All QSPI pins (except SCK) can be used as general-purpose I/O if they are not used by the QSPI while the QSPI is
operating. SCK can only be used for general-purpose I/O if the QSPI is disabled.
2
An output (PCS0) when the QSPI is in master mode.
3
An input (SS) when the QSPI is in slave mode.
4
An input (SS) when the QSPI is in master mode; useful in multimaster systems.
15.6.4 QSPI Operation
The QSPI uses a dedicated 160-byte block of static RAM accessible by both the QSPI and
the CPU to perform queued operations. The RAM is divided into three segments: 32
command control bytes, 64 transmit data bytes, and 64 receive data bytes.
Once the CPU has set up a queue of QSPI commands, written the transmit data segment
with information to be sent, and enabled the QSPI, the QSPI operates independently of the
CPU. The QSPI executes all of the commands in its queue, sets a flag indicating
completion, and then either interrupts the CPU or waits for CPU intervention.
QSPI RAM is organized so that one byte of command data, one word of transmit data, and
one word of receive data correspond to each queue entry, 0x0 to 0x2F.
The CPU initiates QSPI operation by setting up a queue of QSPI commands in command
RAM, writing transmit data into transmit RAM, then enabling the QSPI. The QSPI
executes the queued commands, sets a completion flag (SPIF), and then either interrupts
the CPU or waits for intervention.
There are four queue pointers. The CPU can access three of them through fields in QSPI
registers. The new queue pointer (NEWQP), contained in SPCR2, points to the first
command in the queue. An internal queue pointer points to the command currently being
executed. The completed queue pointer (CPTQP), contained in SPSR, points to the last
command executed. The end queue pointer (ENDQP), contained in SPCR2, points to the
final command in the queue.
15-26
PRELIMINARY—SUBJECT TO CHANGE WITHOUT NOTICE
Table 15-20. QSPI Pin Functions
Mnemonic
MISO
MOSI
1
SCK
PCS[1:3]
PCS0 /
SS
SS
MPC533 Reference Manual
Mode
Master Serial data input to QSPI
Slave Serial data output from QSPI
Master Serial data output from QSPI
Slave Serial data input to QSPI
Master Clock output from QSPI clock
Slave Input to QSPI
Master Outputs select peripheral(s)
Master Output selects peripheral(s)
Slave Input selects the QSPI
Master May cause mode fault
Function
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