AD5292 Analog Devices, AD5292 Datasheet - Page 20

• Manufacturer Part Number: AD5292
• Description: (AD5291 / AD5292) Digital Potentiometer
• Manufacturer: Analog Devices

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AD5291/AD5292
BASIC OPERATION
The basic mode of setting the variable resistor wiper position
(programming the RDAC register) is accomplished by loading
the shift register with Command 1 (see Table 9) and the desired
wiper position data. When the desired wiper position is deter-
mined, the user can load the shift register with Command 3
(see Table 9), which stores the wiper position data in the 20-TP
memory register. After 6 ms, the wiper position is permanently
stored in the 20-TP memory. The RDY pin can be used to moni-
tor the completion of this 20-TP program. Table 10 provides a
programming example, listing the sequence of serial data input
(DIN) words with the serial data output appearing at the SDO
pin in hexadecimal format.
20-TP READBACK AND SPARE MEMORY STATUS
It is possible to read back the contents of any of the 20-TP
memory registers through SDO by using Command 5 (see
Table 9). The lower five LSB bits (D0 to D4) of the data byte
select which memory location is to be read back (see Table 14).
Table 13. Example 20-TP Memory Readback
DIN
0x1414
0x1415
0x0000
0x1410
0x0000
Table 14. Memory Map of Command 5
D9
X
X
X
X
X
…
X
X
X
X
X
1
2
X = don’t care.
Allows the user to calculate the remaining spare memory locations.
D8
X
X
X
X
X
…
X
X
X
X
X
0xXXXX
SDO
0xXXXX
0x03FF
0x00FF
0x0000
D7
X
X
X
X
X
…
X
X
X
X
X
Data Bits [DB9:DB0]
D6
X
X
X
X
X
…
X
X
X
X
X
Action
NOP Instruction 0 sends 16-bit word out of SDO, where the last 10 bits contain the contents of Memory Address 0x10 (17).
Prepares data read from Memory Address 0x14.
Prepares data read from Memory Address 0x15. Sends 16-bit word out of SDO, where the last 10 bits contain the
contents of Memory Address 0x14.
NOP Command 0 sends 16-bit word out of SDO, where last 10-bits contain the contents of Memory Address 0x15.
Prepares data read from memory location 0x10.
D5
X
X
X
X
X
…
X
X
X
X
X
D4
0
0
0
0
0
…
0
0
1
1
1
D3
0
0
0
0
0
…
1
1
0
0
0
1
D2
0
0
0
0
1
…
0
1
0
1
1
D1
0
0
1
1
0
…
0
1
1
0
0
D0
0
1
0
1
0
…
1
0
1
0
1
Register Contents
1
2
3
4
5
…
10
15
20
Programmed memory status (thermometer encoded)
Programmed memory status (thermometer encoded)
st
nd
rd
th
th
Rev. 0 | Page 20 of 28
th
th
th
programmed wiper location (0x00)
programmed wiper location (0x02)
programmed wiper location (0x03)
programmed wiper location (0x04)
programmed wiper location (0x01)
programmed wiper location (0x09)
programmed wiper location (0x0E)
programmed wiper location (0x13)
Data from the selected memory location are clocked out of the
SDO pin during the next SPI operation, where the last 10 bits
contain the contents of the specified memory location.
It is also possible to calculate the address of the most recently
programmed memory location by reading back the contents of
read-only Memory Address 0x14 and Memory Address 0x15
using Command 5. The data bytes read back from Memory
Address 0x014 and Memory Address 0x015 are thermometer
encoded versions of the address of the last programmed
memory location.
For the example outlined in Table 13, the address of the last
programmed location is calculated as
If no memory location has been programmed, then the address
generated is −1.
(Number of Bits = 1 in Memory Address 0x14) + (Number
of Bits = 1 in Memory Address 0x15) − 1 = 10 + 8 − 1 = 17
(0x10)
2
2
(0x14)
(0x15)