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Queued Serial Peripheral Interface (QSPI) Module
MCF5253 Reference Manual, Rev. 1
16-8
Freescale Semiconductor
In wraparound mode, the QSPI cycles through the queue continuously, even while requesting interrupt
service. QDLYR[SPE] is not cleared when the last command in the queue is executed. New receive data
overwrites previously received data in the receive RAM. Each time the end of the queue is reached,
QIR[SPIFE] is set. QIR[SPIF] is not automatically reset. If interrupt driven QSPI service is used, the
service routine must clear QIR[SPIF] to abort the current request. Additional interrupt requests during
servicing can be prevented by clearing QIR[SPIFE].
There are two recommended methods of exiting wraparound mode: clearing QWR[WREN] or setting
QWR[HALT]. Exiting wraparound mode by clearing QDLYR[SPE] is not recommended because this may
abort a serial transfer in progress. The QSPI sets SPIF, clears QDLYR[SPE], and stops the first time it
reaches the end of the queue after QWR[WREN] is cleared. After QWR[HALT] is set, the QSPI finishes
the current transfer, then stops executing commands. After the QSPI stops, QDLYR[SPE] can be cleared.
16.4
QSPI Memory Map and Register Definitions
The programming model for the QSPI consists of six registers. They are the QSPI mode register (QMR),
QSPI delay register (QDLYR), QSPI wrap register (QWR), QSPI interrupt register (QIR), QSPI address
register (QAR), and the QSPI data register (QDR).
There are a total of 80 bytes of memory used for transmit, receive, and control data. This memory is
accessed indirectly using QAR and QDR.
Registers and RAM are written and read by the CPU.
16.4.1
QSPI Mode Register (QMR)
The QMR register, shown in
, determines the basic operating modes of the QSPI module.
Parameters such as clock polarity and phase, baud rate, master mode operation, and transfer size are
determined by this register. The data output high impedance enable, DOHIE, controls the operation of
QSPI_Dout between data transfers. When DOHIE is cleared, QSPI_Dout is actively driven between
transfers. When DOHIE is set, QSPI_Dout assumes a high impedance state.
NOTE
Because the QSPI does not operate in slave mode, the master mode enable
bit, QMR[MSTR], must be set for the QSPI module to operate correctly.
Address MBAR + 0x400
Access: User read/write
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R
MSTR DOHIE
BITS
CPOL CPHA
BAUD
W
Reset
0
0
0
0
0
0
0
1
0
0
0
0
0
1
0
0
Figure 16-3. QSPI Mode Register (QMR)
Содержание MCF5253
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