Programming Examples; Ad5235Eval Evaluation Kit - Analog Devices AD5235 Manual

Because AD5235 can also be supplied by dual supplies, the
general equation defining the output voltage at V
to ground for any given input voltages applied to Terminals A
and B is
D
= × +
V ( D ) V V
W AB
1024
Equation 3 assumes that V
W
wiper resistance is minimized. Operation of the digital potenti-
ometer in divider mode results in more accurate operation over
temperature. Here, the output voltage is dependent on the ratio
of the internal resistors and not the absolute value; therefore, the
drift improves to 15 ppm/°C. There is no voltage polarity
restriction between Terminals A, B, and W as long as the
terminal voltage (V ) stays within V
TERM

PROGRAMMING EXAMPLES

The following programming examples illustrate a typical
sequence of events for various features of the AD5235. See
Table 7 for the instructions and data-word format. The
instruction numbers, addresses, and data appearing at the SDI
and SDO pins are in hexadecimal format.
Table 14. Scratchpad Programming
SDI SDO Action
0xB00100 0xXXXXXX Writes data 0x100 into RDAC1 register,
Wiper W1 moves to 1/4 full-scale
position.
0xB10200 0xB00100 Loads data 0x200 into RDAC2 register,
Wiper W2 moves to 1/2 full-scale
position.
Table 15. Incrementing RDAC Followed by Storing the
Wiper Setting to EEMEM
SDI SDO Action
0xB00100 0xXXXXXX Writes data 0x100 into RDAC1
register, Wiper W1 moves to 1/4 full-
scale position.
0xE0XXXX 0xB00100 Increments RDAC1 register by one to
0x101.
0xE0XXXX 0xE0XXXX Increments RDAC1 register by one to
0x102. Continue until desired wiper
position is reached.
0x20XXXX 0xXXXXXX Stores RDAC2 register data into
EEMEM1. Optionally tie WP to GND to
protect EEMEM values.
The EEMEM values for the RDACs can be restored by power-
on, by strobing the PR pin, or by the two commands shown in
Table 16.
with respect
W
B
is buffered so that the effect of
< V < V .
SS TERM DD
Table 16. Restoring the EEMEM Values to RDAC Registers
SDI SDO
0x10XXXX 0xXXXXXX
0x00XXXX 0x10XXXX
(3)
Table 17. Using Left-Shift by One to Increment 6 dB Steps
SDI SDO
0xC0XXXX 0xXXXXXX
0xC1XXXX 0xC0XXXX
Table 18. Storing Additional User Data in EEMEM
SDI SDO
0x32AAAA 0xXXXXXX
0x335555 0x32AAAA
Table 19. Reading Back Data from Memory Locations
SDI SDO
0x92XXXX 0xXXXXXX
0x00XXXX 0x92AAAA
Table 20. Reading Back Wiper Settings
SDI SDO
0xB00200 0xXXXXXX
0xC0XXXX 0xB00200
0xA0XXXX 0xC0XXXX
0xXXXXXX 0xA003FF

AD5235EVAL EVALUATION KIT

Analog Devices offers a user-friendly AD5235EVAL evaluation
kit that can be controlled by a personal computer through a
printer port. The driving program is self-contained; no
programming languages or skills are needed.
Rev. B | Page 21 of 28
AD5235
Action
Restores the EEMEM1 value to the
RDAC1 register.
NOP. Recommended step to minimize
power consumption.
Action
Moves Wiper 1 to double the
present data contained in the
RDAC1 register.
Moves Wiper 2 to double the
present data contained in the
RDAC2 register.
Action
Stores data 0xAAAA in the extra
EEMEM location USER1. (Allowable to
address in 13 locations with a
maximum of 16 bits of data.)
Stores data 0x5555 in the extra
EEMEM location USER2. (Allowable to
address in 13 locations with a
maximum of 16 bits of data.)
Action
Prepares data read from USER1
EEMEM location.
NOP Instruction 0 sends a 24-bit word
out of SDO, where the last 16 bits
contain the contents in USER1
EEMEM location. The NOP command
ensures that the device returns to the
idle power dissipation state.
Action
Writes RDAC1 to midscale.
Doubles RDAC1 from midscale to full
scale.
Prepares reading wiper setting from
RDAC1 register.
Reads back full-scale value from SDO.