Datasheet
MC68331TS/D 63
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.
*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.
CR[0:F] — Command RAM $YFFD40
7 6543210
CONT BITSE DT DSCK PCS3 PCS2 PCS1 PCS0*
— — — — — — — —
CONT BITSE DT DSCK PCS3 PCS2 PCS1 PCS0*
RECEIVE
RAM
TRANSMIT
RAM
500
51E
520
53E
WORD
540
54F
COMMAND
RAM
BYTEWORD
RR0
RR1
RR2
RRD
RRE
RRF
TR0
TR1
TR2
TRD
TRE
TRF
CR0
CR1
CR2
CRD
CRE
CRF
Freescale Semiconductor, I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
nc
.
..