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Serial Peripheral Interface (SPI)
MC68360 USER’S MANUAL
The following bits should be written by the CPU32+ core before enabling the SPI.
E—Empty
0 = The data buffer associated with this Rx BD has been filled with received data, or
data reception has been aborted due to an error condition. The CPU32+ core is
free to examine or write to any fields of this Rx BD. The CP will not use this BD
again while the E-bit remains zero.
1 = The data buffer associated with this BD is empty, or reception is currently in
progress. This Rx BD and its associated receive buffer are owned by the CP. Once
the E-bit is set, the CPU32+ core should not write any fields of this Rx BD.
Bits 14, 10, 8–2—Reserved
W—Wrap (Final BD in Table)
0 = This is not the last BD in the Rx BD table.
1 = This is the last BD in the Rx BD table. After this buffer has been used, the CP will
receive incoming data into the first BD in the table (the BD pointed to by RBASE).
The number of Rx BDs in this table is programmable and is determined only by the
W-bit and the overall space constraints of the dual-port RAM.
I—Interrupt
0 = No interrupt is generated after this buffer has been filled.
1 = The RXB bit in the SPI event register will be set when this buffer has been com-
pletely filled by the CP, indicating the need for the CPU32+ core to process the
buffer. The RXB bit can cause an interrupt if it is enabled.
CM—Continuous Mode
This bit is valid only when the SPI is configured as a master; it should be written as a zero
in slave mode.
0 = Normal operation.
1 = The E-bit is not cleared by the CP after this BD is closed, allowing the associated
data buffer to be overwritten automatically when the CP next accesses this BD.
This allows continuous reception from an SPI slave into one buffer for autoscan-
ning of a serial A/D peripheral with no CPU overhead.
15
14
13
12
11
10
9876543210
OFFSET + 0
E
—
W
I
L
—
CM
———————
OV
ME
OFFSET + 2
DATA LENGTH
OFFSET + 4
RX DATA BUFFER POINTER
OFFSET + 6
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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