X9455_06 Datasheet, PDF(13/19 Page) Intersil Corporation – Dual Two-wiper Digitally-Controlled Potentiometer

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X9455_06 Datasheet, PDF (13/19 Pages) Intersil Corporation – Dual Two-wiper Digitally-Controlled Potentiometer

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X9455

TABLE 3. REGISTER NUMBERING

STATUS REG (NOTE 1) (Addr: 07H)

REGISTERED SELECTED (NOTE 2)

Reserved

bits 7-3

DRSel1

bit 2

DRSel0

bit 1

NVEnable

bit 0

DCP0

(Addr: 00h)

(Addr: 11h)

DCP2

(Addr: 02h)

(Addr: 01h)

Reserved

WCR0A

WCR0B

WCR1A

WCR1B

DR0A0

DR0B0

DR1A0

DR1B0

DR0A1

DR0B1

DR1A1

DR1B1

DR0A2

DR0B2

DR1A2

DR1B2

DR0A3

DR0B3

DR1A3

DR1B3

NOTES:To read or write the contents of a single Data Register or Wiper Register:

1. Load the status register (using a write command) to select the row. (See Figure 6.)

Writing a 1, 3, 5, or 7 to the Status Register specifies that the subsequent read or write command will access a Data Register. This Status

Register operation also initiates a transfer of the contents of the selected data register to its associated WCR for all DCPs. So, for example,

writing â03hâ to the status register causes the value in DR01 to move to WCR0, DR11 to move to WCR1, DR21 to move to WCR2, and DR31 to

move to WCR3.

Writing a 0 to bit â0â of the Status Register specifies that the subsequent read or write command will access a Wiper Counter Register. Each

WCR can be written to individually, without affecting the contents of any other.

2. Access the desired DR or WCR using a new write or read command (see Figure 7 for write and Figure 9 for read.)

Specify the desired column (DCP number) by sending the DCP address as part of this read or write command.

The registers are organized in pages of four, with one page

consisting of the four volatile WCRs, a second page

consisting of the Level 0 Data Registers, and so forth. These

pages can be written four bytes at time. In this manner all

four potentiometer WCRs can be updated in a single serial

write (see Page Write Operation), as well as all four registers

of a given page in the DR array.

The unique feature of the X9455 device is that writing or

reading to a Data Register of a given wiper automatically

updates the WCR of that wiper with the new value. In this

manner data can be moved from a particular wiper register

to that wiperâs WCR just by performing a 2-wire read

operation. Simultaneously, that data byte can be utilized by

the host.

Status Register Organization

The Status Register (SR) is used in read and write

operations to select the appropriate wiper register. Before

any wiper register can be accessed, the SR must be set to

the correct value. It is accessed by setting the Address Byte

to 07h. See Table 3. Do this by writing the slave address

followed by a byte address of 07h. The SR is volatile and

defaults to 00h on power up. It is an 8-bit register containing

three control bits in the 3 LSBs as follows:

volatile wiper registers if â1â. Table 3 shows this register

organization.

Wiper Addressing for 2-wire Interface

Once the Data Register Level has been selected by a 2-wire

instruction, then the wiper is determined by the Address Byte

of the following instruction. Note again that this enables a

complete page write of all four potentiometers at once a

particular Wiper Register has been chosen. The register

addresses accessible in the X9455 include:

76543

Reserved

WCRSel1

WCRSel0

NVEnable

Bits WCRSel1 and WCRSel0 determine which Data Register

of a wiper is selected for a given operation. NVEnable is

used to select the volatile WCR if â0â, and one of the non

FN8202.1

July 28, 2006

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