Wiper Position

The Wiper Position track bar in the Potentiometer

Control group box is used to change the wiper position

between the H and L end points. Use the computer

mouse or arrow keys to move the Wiper Position

between the 256 position points. The wiper position can

also be changed by entering a numerical value

between 0 and 255 into the H-W Volatile or L-W

Volatile spin boxes, or by pressing the up or down

arrows of these spin boxes. A change in the Wiper

Position track bar, or H-W Volatile/L-W Volatile spin

boxes write to the volatile memory and the wiper posi-

tion is updated with the data sent. The data in the non-

volatile memory remains unchanged. The wiper position

is shown in the H-W Volatile and L-W Volatile spin

boxes. The H-W Volatile spin box shows the wiper

position with respect to the H end point and the L-W

Volatile spin box shows the wiper position with respect

to the L end point. During EV kit power-up, the wiper-

position data in the nonvolatile memory is transferred to

the volatile memory and the position of the wiper is

updated. The H-W Volatile, L-W Volatile, H-W

Nonvolatile, and L-W Nonvolatile spin boxes display

“??” after initializing the EV kit software because the

MAX5422 does not transmit data to the master.

Nonvolatile Programming

The H-W Nonvolatile and L-W Nonvolatile spin boxes

in the Potentiometer Control group box are used to

program the nonvolatile memory of the digital poten-

tiometers. The nonvolatile memory is changed by enter-

ing a numerical value between 0 and 255 into the H-W

Nonvolatile or L-W Nonvolatile spin boxes. The H-W

Nonvolatile spin box shows the wiper position with

respect to the H end point and the L-W Nonvolatile

spin box shows the wiper position with respect to the L

end point. When writing to the nonvolatile memory, the

volatile memory and wiper position remain unchanged.

Volatile/Nonvolatile Data Transferring

The Potentiometer Control group box contains the

Store and Recall buttons used to transfer data from the

volatile memory to the nonvolatile memory and the non-

volatile memory to the volatile memory, respectively.

When the Store button is pressed, the data present in

the volatile memory is transferred to the nonvolatile

memory. When the Recall button is pressed, the data

present in the nonvolatile memory is transferred to the

volatile memory, and the wiper position is updated. The

Store and Recall buttons do not send any new data to

the device because the commands transferred data

already contained in the volatile or nonvolatile memory.

Factory Default

Pressing the Factory Default button resets the wiper

position in the MAX5422 volatile and nonvolatile memo-

ry to the factory-default position. The factory-default

wiper position is the midscale position.

Status Indicator

The Status indicator in the Interface group box dis-

plays EV Kit Operational when the MAX5422 EV kit

enters the normal operating mode after the USB con-

nection is detected. When USB connection is not

detected, or when the software enters the demo mode,

the Status indicator displays Demo Mode.

Command Sent Indicator

The Command Sent indicator in the Interface group

box displays the last command sent from the master

(software) to the MAX5422. There are four commands

available in the MAX5422 IC. Table 1 describes the four

MAX5422 commands.

MAX5422 Evaluation Kit

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5

Table 1. MAX5422 SPI Command

COMMAND

MAX5422 REGISTER

BINARY

HEX

DESCRIPTION

MAX5422 EV KIT

SOFTWARE CONTROL

VREG

00000000

0x00

SPI data is written to VREG

Wiper position updates with SPI data

No change to NVREG

H-W Volatile

L-W Volatile

NVREG

00010000

0x10

SPI data is written to NVREG

No change to wiper position

No change to VREG

H-W Nonvolatile

L-W Nonvolatile

VREGxNVREG

00100000

0x20

Copy VREG to NVREG

No change to wiper position

No change to VREG

Store

NVREGxVREG

00110000

0x30

Copy NVREG to VREG

Wiper position updates with NVREG

No change to NVREG

Recall