CS5529

DS246F5

13

SYNC1

Part of the serial port re-initialization sequence (see text for use of command).

SYNC0

End of the serial port re-initialization sequence.

Read/Write Registers

These commands are used to perform a write to or a read from a specific register. The register to be accessed is

selected with the RSB2-RSB0 bits of the command word.

R/W

0

Write Register

1

Read Register

RSB[4:0]

Register address binary encoded 0 to 31 as follows. All registers are 24 bits long.

Address

Description

000

Read or Write Offset Register

001

Read or Write Gain Register

010

Read or Write Configuration Register

011

Read Conversion Data Register

100

Read or Write Offset Gain and Configuration Registers in

this sequence (i.e. one 8-bit command is followed by 72-bits of

data to access the Offset, then the Gain, and then the

Configuration register)

Serial Port Interface

The CS5529’s serial interface consists of four con-

trol lines: CS, SDI, SDO, and SCLK.

CS, Chip Select, is the control line which enables

access to the serial port. If the CS pin is tied to logic

0, the port can function as a three wire interface.

SDI, Serial Data In, is the data signal used to trans-

fer data to the converters.

SDO, Serial Data Out, is the data signal used to

transfer output data from the converters. The SDO

output will be held at high impedance any time CS

is at logic 1.

SCLK, Serial Clock, is the serial bit-clock which

controls the shifting of data to or from the ADC’s

serial port. The CS pin must be held at logic 0 be-

fore SCLK transitions can be recognized by the

port logic. To accommodate opto-isolators SCLK

is designed with a Schmitt-trigger input to allow an

opto-isolator with slower rise and fall times to di-

rectly drive the pin. Additionally, SDO is capable

of sinking or sourcing up to 5 mA to directly drive

an opto-isolator LED. SDO will have less than a

400 mV loss in the drive voltage when sinking or

sourcing 5 mA.

Figure 4 illustrates the serial sequence necessary to

write to, or read from the serial port’s registers. A

transfer of data is always initiated by sending the

appropriate 8-bit command (MSB first) to the serial

port (SDI pin). It is important to note that some

commands use information from the configuration

registers to perform the function. For those com-

mands it is important that the correct information is

written to the configuration register first.

7

654

32

10

1

111

11

11

7

654

32

10

1

111

11

10

7

654

32

10

10

0

R/W

RSB2

RSB1

RSB0

0