Serial Peripheral Interface (SPI)
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MC68360 USER’S MANUAL
The following status bits are written by the SPI after the received data has been placed into
the associated data buffer.
L—Last
This bit is set by the SPI controller when the buffer is closed due to negation of the SPISEL
pin. This can only occur when the SPI is a slave; otherwise, the ME bit is set.
0 = This buffer does not contain the last character of the message.
1 = This buffer contains the last character of the message.
OV—Overrun
A receiver overrun occurred during reception. This error can only occur when the SPI is a
slave.
ME—Multi-Master Error
This buffer was closed because the SPISEL pin was asserted when the SPI was operating
as a master. This indicates a synchronization problem between multiple masters on the
SPI bus.
Data Length
Data length is the number of octets that the CP has written into this BD’s data buffer. It is
written once by the CP as the BD is closed.
NOTE
The actual amount of memory allocated for this buffer should be
greater than or equal to the contents of the MRBLR.
Rx Data Buffer Pointer
The receive buffer pointer, which always points to the first location of the associated data
buffer, must be even. The buffer may reside in either internal or external memory.
7.12.5.5.2 SPI Transmit Buffer Descriptor (Tx BD). Data to be transmitted with the SPI is
presented to the CP by arranging it in buffers referenced by the Tx BD ring. The first word
of the Tx BD contains status and control bits.
The following bits should be prepared by the user before transmission.
15
14
13
12
11
10
9876543210
OFFSET + 0
R
—
W
I
L
—
CM
———————
UN
ME
OFFSET + 2
DATA LENGTH
OFFSET + 4
TX 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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