Table 3. AUX_ Data-Byte Format (C4 = “1”)

Table 4. Clickless Mode/BIAS_ Data-Byte

Format (C5 = “1”)

2-Wire Serial Interface

serial interface. This protocol consists of an address

byte followed by the command and data bytes. To

address a given chip, the A0 and A1 bits in the

address byte must duplicate the values present at the

A0 and A1 pins of that chip. The rest of the address

bits control MAX4550 operation. The command and

data-byte details are described in the

Command-Byte

and Data-Byte Programming section.

The 2-wire serial interface requires only two I/O lines of

a standard microprocessor port. Figures 1 and 2 detail

the timing diagram for signals on the 2-wire bus, and

Table 5 details the format of the signals. The MAX4550

is a receive-only device and must be controlled by a

bus master device. A bus master device communicates

by transmitting the address byte of the slave device

over the bus and then transmitting the desired informa-

tion. Each transmission consists of a start condition, the

MAX4550’s programmable slave-address byte, a com-

mand-byte, a data-byte, and finally a stop condition.

The slave device acknowledges the recognition of its

address by pulling the SDA line low for one clock peri-

od after the address byte is transmitted. The slave

device also issues a similar acknowledgment after the

command byte and again after the data byte.

Start and Stop Conditions

The bus-master signals the beginning of a transmission

with a start condition by transitioning SDA from high to

low while SCL is high. When the master has finished

communicating with the slave, it issues a stop condition

by transitioning SDA from low to high while SCL is high.

The bus is then free for another transmission.

Slave Address (Address Byte)

The MAX4550 uses an 8-bit-long slave address. To

select a slave address, connect A0 and A1 to V+ or

GND. The MAX4550 has four possible slave addresses,

thus a maximum of four of these devices may share the

same 2-bit address bus. The slave device (MAX4550)

monitors the serial bus continuously, waiting for a start

condition followed by an address byte. When a slave

acknowledges that it is ready for further communication

by pulling the SDA line low while SCL is high.

3-Wire Serial Interface

The MAX4570 3-wire serial interface is SPI/

QSPI/MICROWIRE-compatible. An active-low chip-

select (CS) input enables the device to receive data

from the serial input (DIN). Data is clocked in on the ris-

ing edge of the serial-clock (SCLK) signal. A total of 16

bits are needed in each write cycle. Segmented write

cycles are allowed (two 8-bit-wide transfers) if CS

remains low. The first bit clocked into the MAX4550 is

the command byte’s MSB, and the last bit clocked in is

the data byte’s LSB. While shifting data, the device

remains in its original configuration. After all 16 bits are

clocked into the input shift register, a rising edge on CS

latches the data into the MAX4570 internal registers,

initiating the device’s change of state.

Serially Controlled, Dual 4x2, Clickless

Audio/Video Analog Crosspoint Switches

______________________________________________________________________________________

11

Don’t care

Don’t care

D7

D5

Don’t care

D4

Controls output Q1; 1 = set output high,

0 = set output low.

Don’t care

D6

Controls output Q3; 1 = set output high,

0 = set output low.

D3

D1

Controls output Q0; 1 = set output high,

0 = set output low.

DESCRIPTION

D0

Controls output Q2; 1 = set output high,

0 = set output low.

D2

BIT

Controls COM2A clickless mode; 1 = enables

clickless mode, 0 = disables clickless mode.

Controls COM2B clickless mode; 1 = enables

clickless mode, 0 = disables clickless mode.

D7

D5

Controls COM1A clickless mode; 1 = enables

clickless mode, 0 = disables clickless mode.

D4

Controls COM2A bias resistors; 1 = connect bias

resistors, 0 = disconnect bias resistors.

Controls COM1B clickless mode; 1 = enables

clickless mode, 0 = disables clickless mode.

D6

Controls COM2B bias resistors; 1 = connect bias

resistors, 0 = disconnect bias resistors.

D3

D1

Controls COM1A bias resistors; 1 = connect bias

resistors, 0 = disconnect bias resistors.

DESCRIPTION

D0

Controls COM1B bias resistors; 1 = connect bias

resistors, 0 = disconnect bias resistors.

D2

BIT