Analog Devices Blackfin ADSP-BF537, Hardware Reference Manual

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SPORT Registers
12-58 ADSP-BF537 Blackfin Processor Hardware Reference
SPORTx_TX Register
The SPORTx transmit data register (
SPORTx_TX
) is a write-only register.
Reads produce a Peripheral Access Bus (PAB) error. Writes to this register
cause writes into the transmitter FIFO. The 16-bit wide FIFO is 8 deep
for word length <= 16 and 4 deep for word length > 16. The FIFO is com-
mon to both primary and secondary data and stores data for both. Data
ordering in the FIFO is shown in the
Figure 12-29 . The
SPORTx_TX
regis-
ter is shown in Figure 12-30 .
It is important to keep the interleaving of primary and secondary data in
the FIFO as shown. This means that PAB/DMA writes to the FIFO must
follow an order of primary first, and then secondary, if secondary is
enabled. DAB/PAB writes must match their size to the data word length.
For word length up to and including 16 bits, use a 16-bit write. Use a
32-bit write for word length greater than 16 bits.
Figure 12-29. SPORT Transmit FIFO Data Ordering
0 15
0 15
0 15
0 15
PRIMARY
PRIMARY
PRIMARY
PRIMARY
PRIMARY
PRIMARY
PRIMARY
PRIMARY
W7
W6
W5
W4
W3
W2
W1
W0
PRIMARY
PRIMARY
PRIMARY
PRIMARY
PRIMARY
PRIMARY
PRIMARY
PRIMARY
W3 LOW
W3 HIGH
W2 LOW
W2 HIGH
W1 LOW
W1 HIGH
W0 LOW
W0 HIGH
SECONDARY W3
PRIMARY
PRIMARY
PRIMARY
PRIMARY
PRIMARY
PRIMARY
PRIMARY
PRIMARY
SECONDARY
SECONDARY
SECONDARY
W3
W2
W2
W1
W1
W0
W0
SECONDARY W1 LOW
SECONDARY
SECONDARY
SECONDARY
W1 HIGH
W1 LOW
W1 HIGH
W0 LOW
W0 HIGH
W0 LOW
W0 HIGH
ONLY PRIMARY ENABLED
DATA LENGTH <= 16 BITS
ONLY PRIMARY ENABLED
DATA LENGTH > 16 BITS
8 WORDS OF
PRIMARY DATA
IN FIFO
4 WORDS OF
PRIMARY DATA
IN FIFO
PRIMARY AND
SECONDARY ENABLED
DATA LENGTH <= 16 BITS
PRIMARY AND
SECONDARY ENABLED
DATA LENGTH > 16 BITS
4 WORDS OF
PRIMARY DATA AND
4 WORDS OF
SECONDARY DATA
IN FIFO
2 WORDS OF
PRIMARY DATA AND
2 WORDS OF
SECONDARY DATA
IN FIFO