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DS2890T-000

1-Wire® Digital Potentiometer

Dallas Semiconductor -> Maxim Integrated 

DS2890

READ CONTROL REGISTER [AAH]

The Read Control Register command is used to obtain both the Control Register and potentiometer

Feature Register. Following the Read Control Register command byte, the bus master reads 16 bits to

obtain first the Feature Register byte and then the Control Register byte. The DS2890 will respond with

0’s to additional reads after the 8 bit of the Control Register byte. The Read Control Register command

is terminated with a Reset pulse.

WRITE CONTROL REGISTER [55H]

The Write Control Register command is used to manipulate DS2890 state bits located in the Control

Register. This command is used to set the potentiometer wiper address and charge pump state. The bus

master follows the Write Control Register command byte with an 8-bit register value. Following the 8th

bit of the register byte, the bus master reads back the 8-bit control value from the DS2890 to confirm that

the device received the correct value (Note that if an invalid register value was received by the DS2890,

the bus master will read all 1’s (FFh) during the read back sequence.). If a value other than FFh is read,

the bus master determines if the DS2890 received the correct value. If an incorrect value is read back, the

bus master must issue a Reset pulse and repeat the sequence. If the value read back is correct, the bus

master then sends the 8-bit release code (96h). If the DS2890 accurately receives the release code, the

Control Register is updated and the device will respond with 0’s to additional reads by the bus master. If

an invalid release code is received, no change is made to the Control Register and the device will respond

with 1’s to additional reads by the bus master. The Write Control Register command is terminated with a

Reset pulse.

INCREMENT [C3H]

The Increment command is used for a one step position increase of the currently addressed potentiometer

wiper. Although the DS2890 is a single element potentiometer, wiper addressing still applies and the

Control Register wiper number used for addressing must be set accordingly. The bus master follows the

Increment command byte with an 8-bit read to which the DS2890 will respond with the new 8-bit wiper

position set point. No position change is made if the DS2890 wiper is at the maximum position (FFh)

and an Increment command is received. One difference between the Increment/Decrement commands

and other potentiometer functions is that upon completion of either of these commands, 1-Wire command

processing remains at the potentiometer function level. As shown in Figure 16, additional potentiometer

commands may be sent without going through the ROM function flow.

DECREMENT [99H]

The Decrement command is used for a one step position decrease of the currently addressed

potentiometer wiper. Although the DS2890 is a single element potentiometer, wiper addressing still

applies and the Control Register wiper number used for addressing must be set accordingly. The bus

master follows the Decrement command byte with an 8-bit read to which the DS2890 will respond with

the new 8-bit wiper position set point. No position change is made if the DS2890 wiper is at the

minimum position (00h) and a Decrement command is received. One difference between the

Increment/Decrement commands and other potentiometer functions is that upon completion of either of

these commands, 1-Wire command processing remains at the potentiometer function level. As shown in

Figure 16, additional potentiometer commands may be sent without going through the ROM function

flow.

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