MAX5417L Evaluation Kit/Evaluation System

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5

Nonvolatile Programming

The Non-Volatile edit fields can be used to program the

nonvolatile memory of the digital potentiometer. When

writing to the nonvolatile memory (0x21 command), the

volatile memory and the wiper position remain

unchanged. The Non-Volatile edit fields accept the

numerical position from 0 to 255. The top Non-Volatile

edit field shows the wiper position with respect to the H

end point and the bottom Non-Volatile edit field shows

the wiper position with respect to the L end point.

Volatile/Nonvolatile Data Transfer

The Potentiometer Control box contains buttons

VREG->NVREG and NVREG->VREG that are used to

transfer data from the volatile memory to the nonvolatile

memory and the nonvolatile memory to the volatile mem-

ory. When the VREG->NVREG button is clicked, the data

present in the volatile memory is transferred to the non-

volatile

memory

(0x51

command).

When

the

NVREG->VREG button is clicked, the data present in

the nonvolatile memory is transferred to the volatile mem-

ory (0x61 command) and the wiper position is updated.

These commands do not send any new data to the

device because the commands transfer data already

contained in the volatile or nonvolatile registers.

Interface

The MAX5417L EV kit software automatically searches

for the MAX5417L during startup using the two possible

addresses: 0x50 or 0x52. If the software finds the

MAX5417L digital potentiometer, the Status indicator

shows the MAX5417L is operational or if it is not found,

the Status indicator shows that the MAX5417L was not

found and the Device Address is set to “??”. When

evaluating other versions of the MAX5417 or the

MAX5418/MAX5419 digital potentiometers, use the

Device Type combo box to select the correct device

and select the Auto Detect option from the Device

Address combo box, after starting the MAX5417L EV

kit software.

Use the I2C Bus Speed combo box to set the bus

speed to 400kHz or 100kHz.

There are two methods for communicating with the

MAX5417L EV kit; through the normal user-interface

available through the 2-Wire Interface Diagnostic

(Figure 2) item from the main program’s Options main

such as Read Byte and Write Byte. The Read Byte

operation is not used because the MAX5417L does not

send data to the master. To stop normal user-interface

execution so that it does not override the manually set

values, turn off the update timer by unchecking the

Automatic Diagnostics checkbox in the MAX5417L

main program.

decimal, or hexadecimal. Hexadecimal numbers

should be prefixed by $ or 0x. Binary numbers must be

exactly eight digits. See Figure 2 for an example of this

tool. Figure 2 shows a simple SMBus™ write-byte oper-

ation using the included 2-wire interface diagnostics. In

this example, the software is writing data 0x4E to the

register address 0x11 (volatile memory) of the device

with device address 0x50. The above data sequence

sets the wiper position of the MAX5417L to position 78.

General Troubleshooting

Problem: Software reports it cannot find the board.

• Is the CMODUSB command module power LED

(LED1) lit?

• Is the USB communications cable connected?

• Has Windows plug-and-play detected the board?

Bring up Control Panel, then System, then Device

Manager, and look at what device nodes are indicat-

ed for USB. If there is an “unknown device” node

attached to the USB, delete it. This forces plug-and-

play to try again.

Problem: Unable to find device-under-test (DUT).

• Is power connected to the MAX5417L EV kit?

• Are the SCL and SDA signals pulled up to VDD

through appropriate resistors (2.4kΩ typ)? The

CMODUSB command module dip switch SW1

enables the on-board resistors. There must be pullup

• If using jumper wires to connect, could the SCL and

SDA signals be swapped? Could the ground return

be missing?

SMBus is a trademark of Intel Corporation.