Qspi Ram - Motorola DigitalDNA ColdFire MCF5272 User Manual

Operation
Execution continues at the internal pointer address unless the QWR[NEWQP] value is
changed. After each command is executed, QWR[ENDQP] and QWR[CPTQP] are
compared. When a match occurs, QIR[SPIF] is set and the QSPI stops unless wraparound
mode is enabled. Setting QWR[WREN] enables wraparound mode.
QWR[NEWQP] is cleared at reset. When the QSPI is enabled, execution begins at address
0x0 unless another value has been written into QWR[NEWQP]. QWR[ENDQP] is cleared
at reset but is changed to show the last queue entry before the QSPI is enabled.
QWR[NEWQP] and QWR[ENDQP] can be written at any time. When the QWR[NEWQP]
value changes, the internal pointer value also changes unless a transfer is in progress, in
which case the transfer completes normally. Leaving QWR[NEWQP] and QWR[ENDQP]
set to 0x0 causes a single transfer to occur when the QSPI is enabled.
Data is transferred relative to QSPI_CLK which can be generated in any one of four
combinations of phase and polarity using QMR[CPHA, CPOL]. Data is transferred most
significant bit (msb) first. The number of bits transferred defaults to eight, but can be set to
any value from 8 to 16 by writing a value into the BITSE field of the command RAM,
QCR[BITSE] .

14.4.1 QSPI RAM

The QSPI contains an 80-byte block of static RAM that can be accessed by both the user
and the QSPI. This RAM does not appear in the MCF5272 memory map because it can only
be accessed by the user indirectly through the QSPI address register (QAR) and the QSPI
data register (QDR). The RAM is divided into three segments with 16 addresses each:
• receive data RAM, the initial destination for all incoming data
• transmit data RAM, a buffer for all out-bound data
• command RAM, where commands are loaded
The transmit and command RAM are write-only by the user. The receive RAM is read-only
by the user. Figure 14-2 shows the RAM configuration. The RAM contents are undefined
immediately after a reset.
The command and data RAM in the QSPI is indirectly accessible with QDR and QAR as
48 separate locations that comprise 16 words of transmit data, 16 words of receive data and
16 bytes of commands.
A write to QDR causes data to be written to the RAM entry specified by QAR[ADDR] and
causes the value in QAR to increment. Correspondingly, a read at QDR returns the data in
the RAM at the address specified by QAR[ADDR]. This also causes QAR to increment. A
read access requires a single wait state.
14-4 MCF5272 User's Manual