LTC6948 datasheet(22/38 Pages) AD

22 / 38 page

LTC6948

6948fa

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operaTion

(Addr0) and an LSB of 0 indicating a write. The next byte is

the data intended for the register at address Addr0. CS is

then taken high to terminate the transfer. The first byte of

the second burst contains the destination register address

(Addr1) and an LSB indicating a write. The next byte on

SDI is the data intended for the register at address Addr1.

CS is then taken high to terminate the transfer.

Multiple Byte Transfers

More efficient data transfer of multiple bytes is accom-

plished by using the LTC6948’s register address auto-

increment feature as shown in Figure 11. The serial port

master sends the destination register address in the first

byteanditsdatainthesecondbyteasbefore,butcontinues

sending bytes destined for subsequent registers. Byte 1’s

address is Addr0+1, Byte 2’s address is Addr0+2, and so

on. If the register address pointer attempts to increment

past 14 (h0E), it is automatically reset to 0.

An example of an auto-increment read from the part is

shown in Figure 12. The first byte of the burst sent from

the serial bus master on SDI contains the destination reg-

ister address (Addr0) and an LSB of 1 indicating a read.

Once the LTC6948 detects a read burst, it takes SDO out

of the Hi-Z condition and sends data bytes sequentially,

beginning with data from register Addr0. The part ignores

all other data on SDI until the end of the burst.

Figure 9. Serial Port Read Sequence

Figure 10. Serial Port Single Byte Write

Figure 11. Serial Port Auto-Increment Write

Figure 12. Serial Port Auto-Increment Read

A6 A5 A4 A3 A2

7-BIT REGISTER ADDRESS

Hi-Z

A1 A0 1

D6 D5 D4 D3 D2 D1 D0 DX

8 BITS OF DATA

1 = READ

6948 F09

MASTER–CS

MASTER–SCLK

MASTER–SDI

LTC6948–SDO

16 CLOCKS

ADDR0 + Wr

Hi-Z

MASTER–CS

MASTER–SDI

LTC6948–SDO

BYTE 0

ADDR1 + Wr

BYTE 1

6948 F10

ADDR0 + Wr

Hi-Z

MASTER–CS

MASTER–SDI

LTC6948–SDO

BYTE 0

BYTE 1

BYTE 2

6948 F11

ADDR0 + Rd

DON’T CARE

Hi-Z

MASTER–CS

MASTER–SDI

LTC6948–SDO

6948 F12

BYTE 0

BYTE 1

BYTE 2

LTC6948 Datasheet(PDF) 22 Page - Analog Devices

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