Datasheet

AD5174
Rev. B | 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.
Tabl e 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[DB13:DB10] Data[DB9:DB0]
1
Command
Number
C3 C2 C1 C0 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
Operation
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.
5
2
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.
7
3
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.
1
X is don’t care.
2
See Table 10 for 50-TP memory map.
3
See Table 9 for bit details.