CS5461 datasheet(28/45 Pages) CIRRUS

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CS5461

DS546F2

6. SERIAL PORT OVERVIEW

The CS5461's serial port incorporates a state ma-

chine with transmit/receive buffers. The state ma-

chine interprets 8 bit command words on the rising

edge of SCLK. Upon decoding of the command

word, the state machine performs the requested

command or prepares for a data transfer of the ad-

dressed register. Request for a read requires an in-

ternal register transfer to the transmit buffer, while

a write waits until the completion of 24 SCLKs be-

fore performing a transfer. The internal registers

are used to control the ADC's functions. All regis-

ters are 24-bits in length.

The CS5461 is initialized and fully operational in

its active state upon power-on. After a power-on,

the device will wait to receive a valid command

(the first 8-bits clocked into the serial port). Upon

receiving and decoding a valid command word, the

state machine instructs the converter to either per-

form a system operation, or transfer data to or from

an internal register.

6.1 Commands

All command words are 1 byte in length. Any 8-bit word that is not listed in this section is considered an invalid com-

mand word. Commands that write to a register must be followed by 3 bytes of register data. Commands that read

data can be chained with other commands (e.g., while reading data, a new command can be sent to SDI which can

execute before the original read is completed).

6.1.1 Start Conversions

This command indicates to the state machine to begin acquiring measurements and calculating results. The device

has two modes of acquisition.

C =

Modes of acquisition/measurement

0 = Perform a single computation cycle

1 = Perform continuous computation cycles

6.1.2 SYNC0 Command

This command is the end of the serial port re-initialization sequence. The command can also be used as a NOP

command. The serial port is resynchronized to byte boundaries by sending three or more consecutive SYNC1 com-

mands followed by a SYNC0 command.

6.1.3 SYNC1 Command

This command is part of the serial port re-initialization sequence. The command also serves as a NOP command.

1110

000

11111110

11111111

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