Error Signals and Flags
10-36
ADSP-BF535 Blackfin Processor Hardware Reference
Mode Fault Error (MODF)
The
MODF
bit is set in
SPIx_ST
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
SPIx_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
SPIx_CTL
is cleared, configuring the SPI
interface as a slave
• The
SPE
control bit in
SPIx_CTL
is cleared, disabling the SPI system
• The
MODF
status bit in
SPIx_ST
is set
• An SPI 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. The state of
the input pin is observable in the Flag Clear register (
FIO_FLAG_C)
or the
Flag Set register (
FIO_FLAG_S
).
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 programmable flag registers. This could lead to
contention on the slave select lines if these lines are still driven by the
ADSP-BF535 processor. To ensure that the slave select output drivers are
disabled once a
MODF
error occurs, the program must configure the pro-
grammable flag registers appropriately.
Summary of Contents for ADSP-BF535 Blackfin
Page 80: ...Development Tools 1 26 ADSP BF535 Blackfin Processor Hardware Reference...
Page 312: ...Working With Memory 6 86 ADSP BF535 Blackfin Processor Hardware Reference...
Page 332: ...System Interfaces 7 20 ADSP BF535 Blackfin Processor Hardware Reference...
Page 360: ...Dynamic Power Management Controller 8 28 ADSP BF535 Blackfin Processor Hardware Reference...
Page 446: ...Beginning and Ending an SPI Transfer 10 40 ADSP BF535 Blackfin Processor Hardware Reference...
Page 522: ...Timing Examples 11 76 ADSP BF535 Blackfin Processor Hardware Reference...
Page 562: ...IrDA Support 12 40 ADSP BF535 Blackfin Processor Hardware Reference...
Page 608: ...PCI I O Issues 13 46 ADSP BF535 Blackfin Processor Hardware Reference...
Page 672: ...References 14 64 ADSP BF535 Blackfin Processor Hardware Reference...
Page 810: ...SDRAM Controller SDC 18 86 ADSP BF535 Blackfin Processor Hardware Reference...
Page 811: ...ADSP BF535 Blackfin Processor Hardware Reference 18 87 External Bus Interface Unit...
Page 812: ...SDRAM Controller SDC 18 88 ADSP BF535 Blackfin Processor Hardware Reference...
Page 860: ...DMA Bus Debug Registers 20 30 ADSP BF535 Blackfin Processor Hardware Reference...