adau1461 Analog Devices, Inc., adau1461 Datasheet - Page 45

• Manufacturer Part Number: adau1461
• Description: Sigmadsp Stereo, Low Power, 96 Khz, 24-bit Audio Codec With Integrated Pll Adau1461
• Manufacturer: Analog Devices, Inc.

PROGRAM RAM, PARAMETER RAM, AND DATA RAM
Table 25. RAM Map and Read/Write Modes
Memory
Parameter RAM
Program RAM
Table 25 shows the RAM map (the ADAU1461 register map is
provided in the Control Registers section). The address space
encompasses a set of registers and three RAMs: program,
parameter, and data. The program RAM and parameter RAM
are not initialized on power-up and are in an unknown state
until written to.
PROGRAM RAM
The program RAM contains the 40-bit operation codes that
are executed by the core. The SigmaStudio compiler calculates
maximum instructions per frame for a project and generates an
error when the value exceeds the maximum allowable instructions
per frame based on the sample rate of the signals in the core.
Because the end of a program contains a jump-to-start command,
the unused program RAM space does not need to be filled with
no-operation (NOP) commands.
PARAMETER RAM
The parameter RAM is 32 bits wide and occupies Address 0
to Address 1023. Each parameter is padded with four 0s before
the MSB to extend the 28-bit word to a full 4-byte width. The
data format of the parameter RAM is twos complement, 5.23.
This means that the coefficients can range from +16.0 (minus
1 LSB) to −16.0, with 1.0 represented by the binary word
0000 1000 0000 0000 0000 0000 0000 or by the hexadecimal
word 0x00 0x80 0x00 0x00.
The parameter RAM can be written to directly or with a safe-
load write. The direct write mode of operation is typically used
during a complete new loading of the RAM using burst mode
addressing to avoid any clicks or pops in the outputs. Note that
this mode can be used during live program execution, but because
there is no handshaking between the core and the control port,
the parameter RAM is unavailable to the DSP core during control
writes, resulting in pops and clicks in the audio stream.
SigmaStudio automatically assigns the first eight positions to
safeload parameters; therefore, project-specific parameters start
at Address 0x0008.
The parameter RAM should not be written to until the DSPEN
bit has been set in Register R61 (Address 0x40F5).
DATA RAM
The ADAU1461 data RAM is used to store audio data-words for
processing, as well as certain run-time parameters. SigmaStudio
provides the data and address information for writing to and
reading from the data RAM.
Size
1024 × 32
1024 × 40
Address Range
0 to 1023 (0x0000 to 0x03FF)
2048 to 3071 (0x0800 to 0x0BFF)
Rev. 0 | Page 45 of 88
When implementing blocks, such as delays, that require large
amounts of data RAM space, data RAM utilization should be
taken into account. The SigmaDSP core processes delay times
in one-sample increments; therefore, the total pool of delay
available to the user equals 4096 multiplied by the sample
period. For a f
maximum of about 86 ms, where f
rate. In practice, this much data memory is not available to the
user because every block in a design uses a few data memory
locations for its processing. In most DSP programs, this does
not significantly affect the total delay time. The SigmaStudio
compiler manages the data RAM and indicates whether the
number of addresses needed in the design exceeds the maxi-
mum number available.
READ/WRITE DATA FORMATS
The read/write formats of the control port are designed to be
byte oriented to allow for easy programming of common micro-
controller chips. To fit into a byte-oriented format, 0s are added
to the data fields before the MSB to extend the data-word to
eight bits. For example, 28-bit words written to the parameter
RAM are preceded by four leading 0s to equal 32 bits (four bytes);
40-bit words written to the program RAM are not preceded by
0s because they are already a full five bytes. These zero-padded
data fields are appended to a 3-byte field consisting of a 7-bit
chip address, a read/write bit, and a 16-bit RAM/register address.
The control port knows how many data bytes to expect based
on the address given in the first three bytes.
The total number of bytes for a single-location write command
can vary from one byte (for a control register write) to five bytes
(for a program RAM write). Burst mode can be used to fill
contiguous register or RAM locations. A burst mode write begins
by writing the address and data of the first RAM or register location
to be written. Rather than ending the control port transaction
(by issuing a stop command in I
CLATCH signal high in SPI mode after the data-word), as
would be done in a single-address write, the next data-word
can be written immediately without specifying its address. The
ADAU1461 control port autoincrements the address of each write
even across the boundaries of the different RAMs and registers.
Table 27
and
Read
Yes
Yes
Table 29
S,DSP
of 48 kHz, the pool of available delay is a
Write
Yes
Yes
show examples of burst mode writes.
Write Modes
Direct, safeload
Direct
2
C mode or by bringing the
S,DSP
is the DSP core sampling
ADAU1461