本节介绍在录音路径上实现辅助 ASI 混频器的示例。以下示例代码是在 TAC5112EVM-K 评估模块上使用 PurePath™ Console 3 执行测试。对于辅助 ASI 混频器，器件提供四路输入信号：

• IN1P/IN1M 上的 1kHz、0.2Vrms 差分模拟正弦信号。
• IN2P/IN2M 上的 1kHz、0.5Vrms 差分模拟正弦信号。
• PASI RX 通道 3 上的 500Hz、0.5FS（满标度）数字正弦音调。
• PASI RX 通道 4 输入频率 1.3kHz、0.6FS（满标度）的 PDM 正弦音调。

录音路径上的两个模拟输入信号以及回放路径上的两个数字输入信号均用作输入。混频器的输出信号在辅助 ASI 总线的 DOUT 上发送。

在该示例中，两条 ASI 总线都以 48kHz 的频率运行，因此 SRC 被旁路。图 2-5 所示为相关结果。

#FS refers to Full-Scale
w a0 00 00 #Page 0 
w a0 01 01 #SW Reset
d 01

w a0 00 00 #Page 0 
w a0 02 09 #Exit Sleep Mode with DREG and VREF Enabled
d 10

w a0 1a 30 #PASI in TDM protocol with 32-bit word length
w a0 4d 00 #VREF set to 2.75V for 2Vrms differential fullscale input
w a0 50 00 #ADC Channel 1 configured for AC-coupled differential input with 5kOhm input impedance and audio bandwidth
w a0 55 00 #ADC Channel 2 configured for AC-coupled differential input with 5kOhm input impedance and audio bandwidth

w a0 28 20 #Assign Slot 0 to RX CH1
w a0 29 21 #Assign Slot 1 to RX CH2
w a0 2a 22 #Assign Slot 2 to RX CH3
w a0 2b 23 #Assign Slot 3 to RX CH4

w a0 00 01 #Page 1
w a0 2c 30 #Enable ADC Channel Mixer, Loopback Mixer

#Default ADC Loopback mixer coefficients used
#ADC LB1 = ADC IN1 = 0.2Vrms, 1kHz analog signal (0.1FS)
#ADC LB2 = ADC IN2 = 0.5Vrms, 1kHz analog signal (0.25FS)
#DAC IN3 = 0.5FS, 500Hz signal (0.5FS)
#DAC IN4 = 0.6FS, 1.3kHz signal (0.6FS)

w a0 00 0b #Page 11
#Configure AUX Mixer for OUT1 = 0.3 * ADC LB1 + 0.7 * DAC IN3
w a0 30 2c cc cc cd #x = 0.7

#Configure AUX Mixer for OUT2 = 0.6 * ADC LB2 + 0.4 * DAC IN4
w a0 34 19 99 99 9a #x = 0.4

w a0 00 00 #Page 0
w a0 0a 10 #Configure GPIO1 as GPI
w a0 0b 10 #configure GPIO2 as GPI
w a0 0c 71 #Configure GPIO3 as SASI DOUT
w a0 11 94 #Configure GPIO1 as SASI FSYNC, GPIO2 as SASI BCLK
w a0 18 20 #Enable SASI; Same configurations as PASI

w a0 00 03 #Page 0
w a0 1e 20 #SASI Channel 1 is Channel 1 data
w a0 1f 21 #SASI Channel 2 is Channel 2 data

w a0 00 00 #Page 0
w a0 76 c3 #ADC Channels 1,2 and DAC Channels 3,4 enabled
w a0 78 c0 #ADC, DAC Powered Up