WM8746
Production Data
DAC OUTPUT ATTENUATION
Register bits [7:0] of L0A and R0A control the left and right channel attenuation of DAC 0. Register
bits [7:0] of L1A and R1A control the left and right channel attenuation of DAC 1. Register bits [7:0] of
L2A and R2B control the left and right channel attenuation of DAC 2. Register bits [7:0] of MASTA
are a register that can be used to control attenuation of all channels.
Table 8 shows how the attenuation levels are selected from the 8-bit words.
XA[7:0]
ATTENUATION LEVEL
00(hex)
-∞dB (mute)
01(hex)
-127.5dB
:
:
:
:
:
:
FE(hex)
FF(hex)
-0.5dB
0dB
Table 8 Attenuation Control Levels
EXTENDED INTERFACE CONTROL
It is possible to run the WM8746 channels at different rates with the front two channels running at
twice the rate of the rear four channels. In this mode which is enabled by bit 0 of register 9, the
interface runs at the faster data rate but pin 10 (LRCIN2) acts as the framing LRCIN for the rear
channels see Figure 9.
REGISTER ADDRESS
0001001
BIT
LABEL
DEFAULT
DESCRIPTION
Activates the split rate mode
0: Normal operation
0
2SPD
0
Split rate mode
1: Split rate operation
When the WM8746 receives updates to the volume levels it will, by default, wait for the signal to pass
through the VCAP voltage level before applying the change to the output. This zero cross detect
function ensures that minimal distortion is seen on the output when the volume is changed and is
applied separately to each channel.
REGISTER ADDRESS
0001001
BIT
LABEL
DEFAULT
DESCRIPTION
Controls the ZCD
1
ZCD
0
Zero crossing detect
0: Enabled
1: Disabled
March 2006, PD Rev 4.0
20
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
