AD5171

Rev. D | Page 16 of 24

CONTROLLING THE AD5171

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

program the devices with computer software or employ external

SOFTWARE PROGRAMMING

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

users may consider programming the device in the factory

before shipping it to the end users. Analog Devices offers device

programming software that can be implemented in the factory

on PCs running Windows 95 to Windows XP platforms. As a

result, external controllers are not required, which significantly

reduces development time.

The program is an executable file that does not require the user

to know any programming languages or programming skills. It

is easy to set up and use. Figure 32 shows the software interface.

The software can be downloaded from the AD5171 product page.

Figure 32. Software Interface

Write

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

programming. To increment or decrement the resistance, move

the scrollbar on the left. To write any specific values, use the bit

pattern control in the upper screen and click Run. The format

of writing data to the device is shown in Table 8. Once the

desired setting is found, click Program Permanent to blow the

internal fuse links for permanent setting. The user can also set

the programming bit pattern in the upper screen and click Run

to achieve the same result.

Read

To read the validation bits and data from the device, click Read.

The user may also set the bit pattern in the upper screen and

click Run. The format of reading data out from the device is

shown in Table 9.

DEVICE PROGRAMMING

To apply the device programming software in the factory, users

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

Pin 15, and Pin 25 for SDA_write, SCL, SDA_read, and DGND,

respectively, for the control signals (see Figure 33). In addition,

lay out the PCB of the AD5171 with SCL and SDA pads, as

shown in Figure 34, 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

100Ω

R2

100Ω

R1

100Ω

SDA

READ

WRITE

Figure 33. Parallel Port Connection: Pin 2 = SDA_write, Pin 3 = SCL,

Pin 15 = SDA_read, and Pin 25 = DGND

W

GND

SCL

A

B

AD0

SDA

Figure 34. Recommended AD5171 PCB Layout

Table 8. 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 9. 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