
ADSP-BF59x Blackfin Processor Hardware Reference
15-21
Parallel Peripheral Interface
PPI is using that pin for a
PPI_FSx
frame sync input function. For modes
that do not require
PPI_FS2
, the associated timer is not restricted in func-
tionality and can be operated as if the PPI were not being used (that is, the
TMR1
pin becomes available for timer use as well). For more information
on configuring and using the timers, please refer to the
General-Purpose
Timers
chapter.
In RX mode with 3 external frame syncs, the start of frame detec-
tion occurs where a
PPI_FS2
assertion is followed by an assertion of
PPI_FS1
while
PPI_FS3
is low. This happens at the start of field 1.
Note that
PPI_FS3
only needs to be low when
PPI_FS1
is asserted,
not when
PPI_FS2
asserts. Also,
PPI_FS3
is only used to synchro-
nize to the start of the very first frame after the PPI is enabled. It is
subsequently ignored.
In TX modes with external frame syncs, the
PPI_FS1
and
PPI_FS2
pins are
treated as edge-sensitive inputs. In this mode, it is not necessary to config-
ure the timer(s) associated with the frame sync(s) as input(s), or to enable
them via the
TIMER_ENABLE
register. Additionally, the actual timers them-
selves are available for use, even though the timer pin(s) are taken over by
the PPI. In this case, there is no requirement that the timebase (configured
by
TIN_SEL
in
TIMERx_CONFIG
) be
PPI_CLK
.
However, if using a timer whose pin is connected to an external frame
sync, be sure to disable the pin via the
OUT_DIS
bit in
TIMER_CONFIG
. Then
the timer itself can be configured and enabled for non-PPI use without
affecting PPI operation in this mode. For more information, see the
Gen-
eral-Purpose Timers
chapter.
Programming Model
The following sections describe the PPI programming model.
Содержание ADSP-BF59x Blackfin
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Страница 74: ...Processor Specific MMRs 2 10 ADSP BF59x Blackfin Processor Hardware Reference...
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Страница 738: ...Boundary Scan Architecture B 8 ADSP BF59x Blackfin Processor Hardware Reference...