AD5171

CONTROLLING THE AD5171

There are two ways of controlling the AD5171. Users can either

controllers.

Software Programming

Due to the advantage of the one-time programmable feature,

users may consider programming the device in the factory

before shipping to end users. ADI offers a device programming

software, which can be implemented in the factory on PCs that

run Windows 95 to XP platforms. As a result, external control-

lers are not required, which significantly reduces development

time. The program is an executable file that does not require

any programming languages or user programming skills. It is

easy to set up and use. Figure 33 shows the software interface.

The software can be downloaded from www.analog.com.

Figure 33. AD5171 Computer Software Interface

Write

The AD5171 starts at midscale after power-up prior to the OPT

programming. To increment or decrement the resistance, the

user may simply move the scrollbar on the left. To write any

specific values, the user should use the bit pattern control in the

upper screen and press the Run button. The format of writing

data to the device is shown in Table 7. Once the desirable setting

is found, the user may press the Program Permanent button to

blow the internal fuse links for permanent setting. The user may

also set the programming bit pattern in the upper screen and

press the Run button to achieve the same result.

Read

To read the validation bits and data out from the device, the

user may simply press the Read button. The user may also set

the bit pattern in the upper screen and press the Run button.

The format of reading data out from the device is shown in

Table 8.

To apply the device programming software in the factory, users

need to modify a parallel port cable and configure Pins 2, 3, 15,

and 25 for SDA_write, SCL, SDA_read, and DGND, respectively

for the control signals (Figure 34). Users should also layout the

PCB of the AD5171 with SCL and SDA pads, as shown in

Figure 35, such that pogo pins can be inserted for the factory

programming.

13

25

12

24

11

23

10

22

9

21

8

20

7

19

6

18

5

17

4

16

3

15

2

14

1

SCL

R3

100

Ω

R2

100

Ω

R1

100

Ω

SDA

READ

WRITE

Figure 34. Parallel Port Connection. Pin 2 = SDA_write, Pin 3 = SCL,

Pin 15 = SDA_read, and Pin 25 = DGND

W

DGND

SCL

A

B

AD0

SDA

Figure 35. Recommended AD5171 PCB Layout. The SCL and SDA pads allow

pogo pins to be inserted so that signals can be communicated through the

parallel port for programming (Figure 34).

Table 7. SDA Write Mode Bit Format

S

0

1

0

1

1

0

AD0

0

A

T

X

X

X

X

X

X

X

A

X

X

D5

D4

D3

D2

D1

D0

A

P

Slave Address Byte

Instruction Byte

Data Byte

Table 8. SDA Read Mode Bit Format

S

0

1

0

1

1

0

AD0

1

A

E1

E0

D5

D4

D3

D2

D1

D0

A

P

Slave Address Byte

Data Byte

Rev. PrC | Page 14 of 20

Preliminary Technical Data