
7
Biquads
in
Series
Bass
and
Treble
Loudness
DRC
Input
Mixer
1 Other
Channel Output
From 7 Available
32-Bit
Trunc
PWM
Proc
A_to_ipmix
B_to_ipmix
A
SDIN1
B
C_to_ipmix
D_to_ipmix
SDIN2
Left
Right
Channel Volume
Bass and Treble
Bypass
Bass
and
Treble
Inline
Pre-
Volume
Post-
Volume
Output
Gain
Output Mixer Sums
Any Two Channels
PWM
Output
C
D
Left
Right
DRC
Bypass
DRC
Inline
E_to_ipmix
F_to_ipmix
E
SDIN3
F
G_to_ipmix
H_to_ipmix
SDIN4
Left
Right
G
H
Left
Right
B0016-01
Master
Volume
Max
Volume
2.3.2
I
2C Coefficient Number Formats
2.3.2.1 28-Bit 5.23 Number Format
TAS5508B
8-Channel Digital Audio PWM Processor
www.ti.com
SLES162C – DECEMBER 2005 – REVISED JULY 2009
Figure 2-3. TAS5508B Detailed Channel Processing
The architecture of the TAS5508B is contained in ROM resources within the TAS5508B and cannot be
altered. However, mixer gain, level offset, and filter tap coefficients, which can be entered via the I2C bus
interface, provide a user with the flexibility to set the TAS5508B to a configuration that achieves
system-level goals.
The firmware is executed in a 48-bit, signed, fixed-point arithmetic machine. The most significant bit of the
48-bit data path is a sign bit, and the 47 lower bits are data bits. Mixer gain operations are implemented
by multiplying a 48-bit, signed data value by a 28-bit, signed gain coefficient. The 76-bit, signed output
product is then truncated to a signed, 48-bit number. Level offset operations are implemented by adding a
48-bit, signed offset coefficient to a 48-bit, signed data value. In most cases, if the addition results in
overflowing the 48-bit, signed number format, saturation logic is used. This means that if the summation
results in a positive number that is greater than 0x7FFF FFFF FFFF (the spaces are used to ease the
reading of the hexadecimal number), the number is set to 0x7FFF FFFF FFFF. If the summation results in
a negative number that is less than 0x8000 0000 0000, the number is set to 0x8000 0000 0000.
All mixer gain coefficients are 28-bit coefficients using a 5.23 number format. Numbers formatted as 5.23
numbers have 5 bits to the left of the binary point and 23 bits to the right of the binary point. This is shown
Description
23