WMS7204

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7.8.1 Sending a Command

1. Take the chip out of SLEEP mode.

2. Check that the write protect is set correctly if writing to NVMEM.

3. Check that R/B is HIGH before issuing command.

5. 24 clock pulses are sent for each command. SDI must be valid on the rising edge of the clock,

7. If command 2, 4, 5, 6 or 7 is sent, wait for the R/B pin to go HIGH before sending the next

command.

7.8.2 Wake Up/Sleep/Power Commands

The chip is in SLEEP mode after:

•

•

A Power on Reset command is sent

•

A SLEEP command is sent

Before any operations can be performed the WAKE UP command must be sent.

When a SLEEP command is sent, the chip retains its resistor settings as long as the chip is powered

up but cannot accept any other commands than a WAKE UP command.

TABLE 6 – POWER RELATED COMMANDS

Inst.

No.

Command Name:

Command Byte

Data Byte 1

Data Byte 2

Comment

11

Wake Up

0 0 0 1 x x x x

x x x x x x x x

x x x x x x x x

Wake Up entire chip

10

Sleep

1 0 0 0 x x x x

x x x x x x x x

x x x x x x x x

Send chip into power save

mode

13

Power on Reset

1 0 0 1 x x x x

x x x x x x x x

x x x x x x x x

Reset Chip

1

NOP

0 0 0 0 x x x x

x x x x x x x x

x x x x x x x x

Dummy instruction

The commands above control the entire chip. There is no way to independently power on or off

individual potentiometers.

7.8.3 Write to Tap Register (TR)

The microcontroller can write a value directly into the tap register or send an increment or decrement

command to control the tap register. Alternatively, the contents of an NVMEM location can be written