
PPI Registers
15-32
ADSP-BF59x Blackfin Processor Hardware Reference
The
LT_ERR_UNDR
flag signifies that a horizontal tracking underflow has
occurred, where a new SAV code or
PPI_FS1
assertion occurred before the
value in
PPI_COUNT
was reached.
PPI Delay Count Register (PPI_DELAY)
The
PPI_DELAY
register, shown in
Figure 15-15
, can be used in all config-
urations except ITU-R 656 modes and GP modes with 0 frame syncs. It
contains a count of how many
PPI_CLK
cycles to delay after assertion of
PPI_FS1
before starting to read in or write out data.
Note in TX modes using at least one frame sync, there is a
one-cycle delay beyond what is specified in the
PPI_DELAY
register.
PPI Transfer Count Register (PPI_COUNT)
The
PPI_COUNT
register, shown in
Figure 15-16
, is used in all modes
except “RX mode with 0 frame syncs, external trigger” and “TX mode
with 0 frame syncs.” For RX modes, this register holds the number of sam-
ples to read into the PPI per line, minus one. For TX modes, it holds the
number of samples to write out through the PPI per line, minus one. The
register itself does not actually decrement with each transfer. Thus, at the
beginning of a new line of data, there is no need to rewrite the value of
this register. For example, to receive or transmit 100 samples through the
PPI, set
PPI_COUNT
to 99.
Figure 15-15. PPI Delay Count Register
PPI Delay Count Register (PPI_DELAY)
15 14
13 12 11 10
9
8
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
PPI_DELAY[15:0]
Reset = 0x0000
Number of PPI_CLK cycles to
delay after assertion of
PPI_FS1 before latching in or
sending out data
Содержание ADSP-BF59x Blackfin
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