Serially Controlled, Dual 4x2, Clickless

Audio/Video Analog Crosspoint Switches

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13

Figures 3, 4, and Table 6 show the details of the

3-wire protocol, as it applies to the MAX4570. DOUT is

the shift register’s output. Data at DOUT is simply the

input data delayed by 16 clock cycles, with data

appearing synchronous with SCLK’s falling edge.

Transitions at DIN and SCLK have no effect when CS is

high, and DOUT holds the last bit in the shift register.

Daisy Chaining

To program several MAX4570s, “daisy chain” the

devices by connecting DOUT of the first device to DIN of

the second, and so on. The CS pins of all devices are

connected together, and data is shifted through the

MAX4570s in series. 16 bits of data per device are

required for proper programming of all devices. When

CS is brought high, all devices are updated simultane-

ously.

CS

SCLK

DIN

COMMAND BYTE

DATA BYTE

16

1

C7

D0

C0

D7

Figure 3. 3-Wire Serial-Interface Communication

• • •

• • •

• • •

• • •

CS

SCLK

DIN

DOUT

Figure 4. 3-Wire Serial-Interface Timing Details