ADSP-BF537 Blackfin Processor Hardware Reference
7-13
Parallel Peripheral Interface
Because all H and V signalling is embedded in the datastream in ITU-R
656 modes, the
PPI_COUNT
register is not necessary. However, the
PPI_FRAME
register is used in order to check for synchronization errors.
The user programs this MMR for the number of lines expected in each
frame of video, and the PPI keeps track of the number of EAV-to-SAV
transitions that occur from the start of a frame until it decodes the
end-of-frame condition (transition from F = 1 to F = 0). At this time, the
actual number of lines processed is compared against the value in
PPI_FRAME
. If there is a mismatch, the
FT_ERR
bit in the
PPI_STATUS
regis-
ter is asserted. For instance, if an SAV transition is missed, the current
field will only have
NUM_ROWS – 1
rows, but resynchronization will reoccur
at the start of the next frame.
Upon completing reception of an entire field, the field status bit is toggled
in the
PPI_STATUS
register. This way, an interrupt service routine (ISR)
can discern which field was just read in.
General-Purpose PPI Modes
The General-Purpose (GP) PPI modes are intended to suit a wide variety
of data capture and transmission applications.
summarizes these
modes. If a particular mode shows a given
PPI_FSx
frame sync not being
used, this implies that the pin is available for its alternate, multiplexed
functions.
Table 7-4. General-Purpose PPI Modes
GP PPI Mode
PPI_FS1
Direction
PPI_FS2
Direction
PPI_FS3
Direction
Data
Direction
RX mode, 0 frame syncs, external
trigger
Input
Not used
Not used
Input
RX mode, 0 frame syncs, internal
trigger
Not used
Not used
Not used
Input
RX mode, 1 external frame sync
Input
Not used
Not used
Input
Summary of Contents for Blackfin ADSP-BF537
Page 42: ...Contents xlii ADSP BF537 Blackfin Processor Hardware Reference ...
Page 90: ...Development Tools 1 32 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 138: ...Programming Examples 4 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 340: ...SDC Programming Examples 6 84 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 606: ...Programming Examples 9 94 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 660: ...Programming Examples 10 54 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 720: ...Electrical Specifications 11 60 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 840: ...Programming Examples 13 42 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 876: ...Programming Examples 14 36 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 938: ...Programming Examples 15 62 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 958: ...Programming Examples 17 12 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 986: ...Programming Examples 18 28 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 1162: ...G 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 1218: ...Index I 56 ADSP BF537 Blackfin Processor Hardware Reference ...