6 pga auxiliary analog output, 7 control port description and timing, 1 spi mode – Cirrus Logic CS5346 User Manual

Page 23: Cs5346

DS861PP3

CS5346

5.6

PGA Auxiliary Analog Output

The CS5346 includes an auxiliary analog output through the PGAOUT pins. These pins can be configured

to output the analog input to the ADC as selected by the input MUX and gained or attenuated with the PGA,

or alternatively, they may be set to high impedance. See the

for

information on configuring the PGA auxiliary analog output.

The PGA auxiliary analog output can source very little current. As current from the PGAOUT pins increases,

distortion will increase. For this reason, a high-input impedance buffer must be used on the PGAOUT pins

to achieve full performance. An example buffer for PGAOUT is provided on the CDB5346 for reference. Re-

fer to the table in

for acceptable loading conditions.

5.7

Control Port Description and Timing

The control port is used to access the registers, allowing the CS5346 to be configured for the desired oper-

ational modes and formats. The operation of the control port may be completely asynchronous with respect

to the audio sample rates. However, to avoid potential interference problems, the control port pins should

remain static if no operation is required.

The control port has two modes: SPI and I²C, with the CS5346 acting as a slave device. SPI Mode is se-

lected if there is a high-to-low transition on the AD0/CS pin, after the RST pin has been brought high. I²C

Mode is selected by connecting the AD0/CS pin through a resistor to VLC or DGND, thereby permanently

selecting the desired AD0 bit address state.

5.7.1

SPI Mode

In SPI Mode, CS is the chip-select signal; CCLK is the control port bit clock (input into the CS5346 from

the microcontroller); CDIN is the input data line from the microcontroller; CDOUT is the output data line

to the microcontroller. Data is clocked in on the rising edge of CCLK and out on the falling edge.

shows the operation of the control port in SPI Mode. To write to a register, bring CS low. The

first seven bits on CDIN form the chip address and must be 1001111. The eighth bit is a read/write indi-

cator (R/W), which should be low to write. The next eight bits form the Memory Address Pointer (MAP),

which is set to the address of the register that is to be updated. The next eight bits are the data that will

be placed into the register designated by the MAP. During writes, the CDOUT output stays in the Hi-Z

state. It may be externally pulled high or low with a 47 k resistor, if desired.

To read a register, the MAP has to be set to the correct address by executing a partial write cycle which

finishes (CS high) immediately after the MAP byte. To begin a read, bring CS low, send out the chip ad-