Low-Cost 4x4, 8x4, 8x8

Video Crosspoint Switches

8

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32-Bit Serial-Interface Mode (MAX4456)

are loaded with data, making it unnecessary to specify

an output address (A2, A1, A0). The input data format

is D3–D0, starting with OUT0 and ending with OUT7 for

32 total bits. Only codes 0000 through 1010 are valid.

Code 1010 disables a buffer, while code 1001 enables

it. After data is shifted into the 32-bit first-rank register, it

is transferred to the second rank by LATCH (Table 2),

which updates the switches.

SERIAL /

PARALLEL

D3

H

X

L

H

L

(A2), A1,

A0

X

Output

Buffer

Address

Output

Buffer

Address

D1

Serial

Output

Parallel

Input

Parallel

Input

D2

X

Parallel

Input

Parallel

Input

D0

Serial Input

Parallel

Input

Parallel

Input

COMMENT

Serial Mode

Parallel Mode,

D0–D2 = Control Code

Parallel Mode,

D0–D2 = Input Address

L

Table 3. Input/Output Line Configurations

X = Don’t care, H = 5V, L = 0V

( ) are for MAX4456 only.

Table 2. Serial-Interface Mode Functions

D3–D0

FUNCTION

0000 to 0111

Connect the selected buffer to the input

channel selected by D3–D0. Note that 0100

through 0111 are not valid for the MAX4359.

1000

Connect the input of the selected buffer to

GND. Note: If the buffer output remains

on, its input is its offset voltage.

1001

Turn on the selected buffer and connect

its input to GND. Use this code to turn on

buffers after power is applied. The default

power-up state is all buffers disabled.

1010

Shut off the selected buffer at the speci-

fied channel, and erase data stored in the

2nd rank of registers. The 2nd rank now

holds the command word 1010.

1011 to 1111

Do not use these codes in the serial-inter-

face mode. They inhibit the latching of the

2nd-rank registers, which prevents proper

data loading.