ADSP-BF50x Blackfin Processor Hardware Reference
18-41
SPI-Compatible Port Controller
Mode Fault Error (MODF)
The MODF bit is set in SPI_STAT when the SPISS input pin of a device
enabled as a master is driven low by some other device in the system. This
occurs in multimaster systems when another device is also trying to be the
master. To enable this feature, the PSSE bit in SPI_CTL must be set. This
contention between two drivers can potentially damage the driving pins.
As soon as this error is detected, these actions occur:
• The
MSTR
control bit in
SPI_CTL
is cleared, configuring the SPI
interface as a slave
• The
SPE
control bit in
SPI_CTL
is cleared, disabling the SPI system
• The
MODF
status bit in
SPI_STAT
is set
• An SPI error interrupt is generated
These four conditions persist until the
MODF
bit is cleared by software.
Until the
MODF
bit is cleared, the SPI cannot be re-enabled, even as a slave.
Hardware prevents the user from setting either
SPE
or
MSTR
while
MODF
is
set.
When
MODF
is cleared, the interrupt is deactivated. Before attempting to
re-enable the SPI as a master, the state of the
SPISS
input pin should be
checked to make sure the pin is high. Otherwise, once
SPE
and
MSTR
are
set, another mode fault error condition immediately occurs.
When
SPE
and
MSTR
are cleared, the SPI data and clock pin drivers (
MOSI
,
MISO
, and
SCK
) are disabled. However, the slave select output pins revert to
being controlled by the general-purpose I/O port registers. This could lead
to contention on the slave select lines if these lines are still driven by the
processor. To ensure that the slave select output drivers are disabled once
an
MODF
error occurs, the program must configure the general-purpose I/O
port registers appropriately.
When enabling the
MODF
feature, the program must configure as inputs all
of the port pins that will be used as slave selects. Programs can do this by
Summary of Contents for EZ-KIT Lite ADSP-BF506F
Page 50: ...Contents l ADSP BF50x Blackfin Processor Hardware Reference ...
Page 92: ...Development Tools 1 30 ADSP BF50x Blackfin Processor Hardware Reference ...
Page 110: ...Interface Overview 3 12 ADSP BF50x Blackfin Processor Hardware Reference ...
Page 236: ...Internal Flash Memory Control Registers 6 92 ADSP BF50x Blackfin Processor Hardware Reference ...
Page 650: ...Programming Examples 15 56 ADSP BF50x Blackfin Processor Hardware Reference ...
Page 804: ...Programming Examples 17 92 ADSP BF50x Blackfin Processor Hardware Reference ...
Page 1194: ...Programming Examples 24 90 ADSP BF50x Blackfin Processor Hardware Reference ...
Page 1256: ...ACM Registers A 50 ADSP BF50x Blackfin Processor Hardware Reference ...
Page 1264: ...Boundary Scan Architecture B 8 ADSP BF50x Blackfin Processor Hardware Reference ...