WMS7140/1

- 8 -

The Up/Down family has a 3-wire Serial Data Interface consisting of CS , INC , U/ D pins. Only

UP/DOWN operations can be performed. The key features of this interface include:

•

Increment/Decrement operations on the tap register (TR)

•

Direct refresh of tap register (TR) from internal NVMEM

•

Nonvolatile storage of the present tap register value into the NVMEM and automatic recall at

power up

•

For WMS7141 devices, output buffer amplifier

The wiper position or the Tap Register(TR) setting can only be changed by the UP/DOWN operation

down when U/ D is Low. The TR setting will be stored into the user NVMEM automatically each time

CS

goes high while INC holds high. Otherwise, if INC is low when CS goes high, the TR setting

will not be stored. The NVMEM content will be automatically loaded into TR at Power On. The user

NVMEM can be tested through the voltage measurement on the wiper pin after saving TR setting into

the NVMEM and reloading into the TR. When the TR setting is already at LOW, further DOWN

operations won’t change the setting. Similarly, when TR setting is at HIGH, further UP operations

won’t change the setting.

When CS is held HIGH, the part will be in Standby mode and the TR setting will not be changed.

The operating modes of Up/Down are summarized below.

CS

U/ D

INC

Operation

Low

High

High to Low

Low

Low

High to Low

Low to High

x

High

Store Wiper Position

Low to High

x

Low

No Store, Return to Standby

High

x

x

Standby

Note: x means don’t care