MPC555
/
MPC556
QUEUED SERIAL MULTI-CHANNEL MODULE
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
14-18
14.7.1.2 QSPI Control Register 1
SPCR1 enables the QSPI and specifies transfer delays. The CPU has read/write ac-
cess to SPCR1, but the QSPI has read access only to all bits except SPE. SPCR1
must be written last during initialization because it contains SPE. The QSPI automati-
cally clears this bit after it completes all serial transfers or when a mode fault occurs.
Writing a new value to SPCR1 while the QSPI is enabled disrupts operation.
14.7.1.3 QSPI Control Register 2
SPCR2 contains QSPI queue pointers, wraparound mode control bits, and an interrupt
enable bit. The CPU has read/write access to SPCR2, but the QSPI has read access
only. Writes to this register are buffered. New SPCR2 values become effective only
after completion of the current serial transfer. Rewriting NEWQP in SPCR2 causes ex-
ecution to restart at the designated location. Reads of SPCR2 return the current value
of the register, not the buffer.
SPCR1 —
QSPI Control Register 1
0x30 501A
MSB
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
LSB
15
SPE
DSCKL
DTL
RESET:
0
0
0
0
0
1
0
0
0
0
0
0
0
1
0
0
Table 14-15 SPCR1 Bit Descriptions
Bit(s)
Name
Description
0
SPE
QSPI enable. Refer to
14.7.4.1 Enabling, Disabling, and Halting the SPI
0 = QSPI is disabled. QSPI pins can be used for general-purpose I/O.
1 = QSPI is enabled. Pins allocated by PQSPAR are controlled by the QSPI.
1:7
DSCKL
Delay before SCK. When the DSCK bit is set in a command RAM byte, this field determines the
length of the delay from PCS valid to SCK transition. The following equation determines the ac-
tual delay before SCK:
where DSCKL equals is in the range of 1 to 127.
14.7.5.3 Delay Before Transfer
for more information.
8:15
DTL
Length of delay after transfer. When the DT bit is set in a command RAM byte, this field deter-
mines the length of the delay after a serial transfer. The following equation is used to calculate
the delay:
where DTL is in the range of 1 to 255.
A zero value for DTL causes a delay-after-transfer value of 8192
÷
F
SYS
(204.8 µs with a 40-MHz
IMB clock).
for more information.
PCS to SCK Delay
DSCKL
f
SYS
--------------------
=
Delay after Transfer
32 D
×
TL
f
SYS
------------------------
=
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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