DS2890

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RESUME COMMAND [A5H]

In a typical application the DS2890 may be accessed several times to complete a control adjustment. In a

multi-drop environment this means that the 64-bit ROM sequence of a Match ROM command has to be

repeated for every access. To maximize the data throughput in a multi-drop environment the Resume

Command function was implemented. As shown in Figure 19, this function checks the status of the RC

flag and, if it is set, directly transfers control to the potentiometer functions, similar to a Skip ROM

command. The only way to set the RC flag is through successfully executing the Match ROM, Search

ROM, Conditional Search ROM, or Overdrive Match ROM command. Once the RC flag is set, the

device can repeatedly be accessed through the Resume Command function. Accessing another device on

the bus will clear the RC flag, preventing two or more devices from simultaneously responding to the

Resume Command function.

POTENTIOMETER FUNCTION EXAMPLE

position to mid-point, increment the wiper twice, and decrement the wiper once.

MASTER MODE

DATA (LSB FIRST)

COMMENTS

TX

Reset

Reset Pulse (480 - 960

µs)

RX

Presence

Presence Pulse

TX

CCh

Issue Skip ROM Command

TX

55h

Issue Write Control Register Command

TX

4Ch

Issue Control Register value for WN=0, CPC=1

RX

<data byte>

Read back Control Register value (4Ch) and verify

TX

96h

Issue Release Code to update Control Register

RX

<data bits>

If 0’s are read, update was successful; if 1’s are read,

the update failed

TX

Reset

Reset Pulse (480 - 960

µs)

RX

Presence

Presence Pulse

TX

CCh

Issue Skip ROM Command

TX

0Fh

Issue Write Position Command

TX

7Fh

Write Wiper Position value

RX

<data byte>

Read back Wiper Position byte and verify

TX

96h

Issue Release Code to update Wiper Position

RX

<data bits>

If 0’s are read, update was successful; if 1’s are read,

the update failed

TX

Reset

Reset Pulse

RX

Presence

Presence Pulse

TX

CCh

Issue Skip ROM Command