
PRELIMINARY TECHNICAL DATA
Nonvolatile Memory Programmable Resistors
ADN2850
REV PrH, 13, AUG 2001
13
PROGRAMMING EXAMPLES
The following programming examples illustrate typical sequence
of events for various features of the ADN2850. Users should
refer to Table 2 for the instructions and data word format. The
Instruction numbers, addresses, and data appearing at SDI and
SDO pins are based in hexadecimal in the following examples.
SDI
SDO
Action
B00100
H
XXXXXX
H
Loads data 100
H
into RDAC1 register, Wiper
W1 moves to 1/4 full-scale position
B10200
H
B00100
H
Loads data 200
H
into RDAC2 register, Wiper 2
moves to 1/2 full-scale position
Example 1. Set two programmable resistors to independent data
SDI
SDO
Action
B00100
H
XXXXXX
H
Loads data 100
H
into RDAC1 register, Wiper
W1 moves to 1/4 full-scale position
E0XXXX
H
B00100
H
Increments RDAC1 register by one to 101
H
E0XXXX
H
E0XXXX
H
Increments RDAC1 register by one to 102
H
Continue until desired wiper position reached
20XXXX
H
XXXXXX
H
Saves RDAC1 register data into EEMEM1
Optionally tie
WP
to GND to protect EEMEM values
Example 2. Incrementing one programmable resistor followed by
storing the wiper setting to EEMEM
EEMEM values for RDACs can be restored by
Power On or
Strobing
PR
pin or
Programming shown below
SDI
SDO
Action
10XXXX
H
XXXXXX
H
Restores EEMEM1 value to RDAC1
register
00XXXX
H
10XXXXX
H
NOP. Recommended step to minimize
power consumption
8XXXXX
H
00XXXX
H
Restores EEMEM1 and EEMEM2 values to
RDAC1 and RDAC2 registers respectively
Example 3. Restoring EEMEM values to RDAC registers
SDI
SDO
Action
C0XXXX
H
XXXXXX
H
Moves wiper #1 to double the present data
contained in RDAC1 register
C1XXXX
H
C0XXXX
H
Moves wiper #2 to double the present data
contained in RDAC2 register.
Example 4. Using Left shift by one to increment +6dB steps
SDI
SDO
Action
32AAAA
H
XXXXXX
H
Stores data AAAA
H
into spare EEMEM
location USER1 (Allowable to address in 13
locations with maximum 16-bits of Data)
335555
H
32AAAA
H
Stores data 5555
H
into spare EEMEM
location USER2. (Allowable to address 13
locations with maximum 16-bits of Data)
Example 5. Storing additional user data in EEMEM
SDI
SDO
Action
92XXXX
H
XXXXXX
H
Prepares data read from USER1 location
00XXXX
H
92AAAA
H
NOP instruction #0 sends 24-bit word out of
SDO where the last 16 bits contain the
contents
of USER1 location. NOP
command insures device returns to idle
power dissipation state
Example 6. Reading back data from various memory locations
SDI
SDO
Action
B00200
H
XXXXXX
H
Sets RDAC1 to mid-scale
C0XXXX
H
B00200
H
Doubles RDAC1 from mid-scale to full
scale
A0XXXX
H
C0XXXX
H
Prepares reading wiper setting from RDAC1
register
XXXXXX
H
A003FF
H
Readback full scale value from RDAC1
register.
Example 7. Reading back wiper setting
Analog Devices offers a user friendly ADN2850EVAL
evaluation kit and it can be controlled by a personal computer
through the printer port.