AD5174

Rev. 0 | Page 13 of 20

RDAC AND 50-TP READ OPERATION

A serial data output SDO pin is available for readback of

the internal RDAC register or 50-TP memory contents. The

contents of the RDAC register can be read back through

SDO by using Command 2 (see Table 6). Data from the

RDAC register is clocked out of the SDO pin during the last

10 clocks of the next SPI operation.

It is possible to read back the contents of any of the 50-TP

memory registers through SDO by using Command 5. The

lower six LSB bits, D5 to D0 of the data byte, select which

memory location is to be read back, as shown in Table 10.

Data from the selected memory location is clocked out of the

SDO pin during the next SPI operation. A binary encoded version

address of the most recently programmed wiper memory location

can be read back using Command 6 (see Table 6). This can be used

to monitor the spare memory status of the 50-TP memory block.

Table 7 provides a sample listing for the sequence of serial data

input (DIN) words with the serial data output appearing at the

SDO pin in hexadecimal format for a write and read to both the

RDAC register and the 50-TP memory (Memory Location 20).

Table 6. Command Operation Truth Table

Command

Number

Command[DB13:DB10]

Data[DB9:DB0]1

Operation

C3

C2

C1

C0

D9

D8

D7

D6

D5

D4

D3

D2

D1

D0

0

0

0

0

0

X

X

X

X

X

X

X

X

X

X

NOP: do nothing.

1

0

0

0

1

D9

D8

D7

D6

D5

D4

D3

D2

D1

D0

Write contents of serial register

data to RDAC.

2

0

0

1

0

X

X

X

X

X

X

X

X

X

X

Read contents of RDAC wiper

register.

3

0

0

1

1

X

X

X

X

X

X

X

X

X

X

Store wiper setting: store RDAC

setting to 50-TP.

4

0

1

0

0

X

X

X

X

X

X

X

X

X

X

Software reset: refresh RDAC with

last 50-TP memory stored value.

52

0

1

0

1

X

X

X

X

D5

D4

D3

D2

D1

D0

Read contents of 50-TP from SDO

output in the next frame.

6

0

1

1

0

X

X

X

X

X

X

X

X

X

X

Read address of last 50-TP

programmed memory location.

73

0

1

1

1

X

X

X

X

X

X

X

X

D1

D0

Write contents of serial register

data to control register.

8

1

0

0

0

X

X

X

X

X

X

X

X

X

X

Read contents of control register.

9

1

0

0

1

X

X

X

X

X

X

X

X

X

D0

Software shutdown.

D0 = 0; normal mode.

D0 = 1; device placed in shutdown

mode.

2 See Table 10 for 50-TP memory map.