adau1781bcpz-rl Analog Devices, Inc., adau1781bcpz-rl Datasheet - Page 36

• Manufacturer Part Number: adau1781bcpz-rl
• Description: Low Noise Stereo Codec With Sigmadsp Processing Core
• Manufacturer: Analog Devices, Inc.

ADAU1781
SPI PORT
By default, the ADAU1781 is in I
control mode by pulling CLATCH low three times. The SPI port
uses a 4-wire interface, consisting of CLATCH , CCLK, CDATA,
and COUT signals, and is always a slave port. The CLATCH signal
goes low at the beginning of a transaction and high at the end of
a transaction. The CCLK signal latches CDATA on a low-to-high
transition. COUT data is shifted out of the ADAU1781 on the
falling edge of CCLK and should be clocked into a receiving
device, such as a microcontroller, on the CCLK rising edge. The
CDATA signal carries the serial input data, and the COUT signal is
the serial output data. The COUT signal remains three-stated until
a read operation is requested. This allows other SPI-compatible
peripherals to share the same readback line. All SPI transactions
have the same basic format shown in
is shown in
ADAU1781 can be taken out of SPI mode only by a full reset.
Chip Address R/ W
The first byte of an SPI transaction includes the 7-bit chip address
and an R/ W bit. The chip address is always 0x38. The LSB of
this first byte determines whether the SPI transaction is a read
(Logic 1) or a write (Logic 0).
Table 23. SPI Address Byte Format
Bit 0
0
Subaddress
The 12-bit subaddress word is decoded into a location in one of
the registers. This subaddress is the location of the appropriate
register. The MSBs of the subaddress are zero-padded to bring the
word to a full 2-byte length.
Table 24. Generic Control Word Format
Byte 0
CHIP_ADR[6:0], R/W
1
Continues to end of data.
Bit 1
1
Figure 4
Bit 2
1
. All data should be written MSB first. The
Bit 3
1
2
C mode, but can be put into SPI
Bit 4
0
Table 24
Byte 1
SUBADR[15:8]
Bit 5
0
. A timing diagram
Bit 6
0
Bit 7
R/W
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Byte 2
SUBADR[7:0]
Data Bytes
The number of data bytes varies according to the register being
accessed. During a burst mode write, an initial subaddress is
written followed by a continuous sequence of data for consecutive
register locations. A sample timing diagram for a single-write
SPI operation to the parameter memory is shown in Figure 43.
A sample timing diagram of a single-read SPI operation is shown
in Figure 44. The COUT pin goes from three-state to being driven
at the beginning of Byte 3. In this example, Byte 0 to Byte 2
contain the addresses and R/ W bit, and subsequent bytes carry
the data.
SPI Read/Write Clock Frequency (CCLK)
The SPI port of the ADAU1781 has asymmetrical read and
write clock frequencies. It is possible to write data into the
device at higher data rates than reading data out of the device.
More detailed information is available in the Digital Timing
Specifications section.
MEMORY AND REGISTER ACCESS
Several conditions must be true to have full access to all memory
and registers via the control port:
•
•
•
•
The ADAU1781 must have finished its initialization,
including power-on reset, PLL lock, and self-boot.
The core clock must be enabled (Register 16384 (0x4000),
clock control, Bit 0, core clock enable, set to 1).
The memory controller must be powered (Register 16512
(0x4080), Digital Power-Down 0, Bit 6, memory controller,
set to 1).
The SigmaDSP core must be powered (Register 16512
(0x4080), Digital Power-Down 0, Bit 0, SigmaDSP core,
set to 1).
Byte 3
Data
Byte 4
Data
1