MC68CK331CAG16 Datasheet, PDF (63/84 Pages) Freescale Semiconductor, Inc – 32-Bit Modular Microcontroller

Freescale Semiconductor, Inc.
500
RR0
RR1
RR2
RECEIVE
RAM
RRD
RRE
51E
RRF
WORD
520
TR0
TR1
TR2
TRANSMIT
RAM
TRD
TRE
53E
TRF
540
CR0
CR1
CR2
COMMAND
RAM
CRD
CRE
54F
CRF
WORD
BYTE
Figure 14 QSPI RAM
Once the CPU has set up the queue of QSPI commands and enabled the QSPI, the QSPI can operate
independently of the CPU. The QSPI executes all of the commands in its queue, sets a flag indicating
that it is finished, and then either interrupts the CPU or waits for CPU intervention. It is possible to ex-
ecute a queue of commands repeatedly without CPU intervention.
RR[0:F] — Receive Data RAM
$YFFD00
Data received by the QSPI is stored in this segment. The CPU reads this segment to retrieve data from
the QSPI. Data stored in receive RAM is right-justified. Unused bits in a receive queue entry are set to
zero by the QSPI upon completion of the individual queue entry. The CPU can access the data using
byte, word, or long-word addressing.
The CPTQP value in SPSR shows which queue entries have been executed. The CPU uses this infor-
mation to determine which locations in receive RAM contain valid data before reading them.
TR[0:F] — Transmit Data RAM
$YFFD20
Data that is to be transmitted by the QSPI is stored in this segment. The CPU usually writes one word
of data into this segment for each queue command to be executed.
Information to be transmitted must be written to transmit data RAM in a right-justified format. The QSPI
cannot modify information in the transmit data RAM. The QSPI copies the information to its data serial-
izer for transmission. Information remains in transmit RAM until overwritten.
CR[0:F] — Command RAM
7
6
5
CONT
BITSE
DT
4
DSCK
3
PCS3
2
PCS2
$YFFD40
1
PCS1
0
PCS0*
—
—
—
—
—
—
—
—
CONT
BITSE
DT
DSCK
PCS3
PCS2
PCS1
PCS0*
*The PCS0 bit represents the dual-function PCS0/SS.
Command RAM is used by the QSPI when in master mode. The CPU writes one byte of control infor-
mation to this segment for each QSPI command to be executed. The QSPI cannot modify information
in command RAM.
MC68331TS/D
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