es the associated switch (Table 2). A logic “0” in any
data-bit location opens the associated switch.
2-Wire Serial Interface
The MAX4584 uses a 2-wire I
2
C-compatible serial inter-
face. The COM_ register uses the “SendByte” protocol,
which consists of an address byte followed by a com-
mand byte (Table 1).
To address a given IC, bit A in the address byte must
duplicate the value present at the A pin of that IC. The
rest of the address bits must match those shown in
Table 3. The command byte details are described in
the
Switch Control
section.
The 2-wire serial interface requires only two I/O lines of
a standard microprocessor (µP) port. Figures 1 and 2
detail the timing diagram for signals on the 2-wire bus,
and Tables 1 and 3 detail the format of the signals. The
MAX4584 is a receive-only device and must be con-
trolled by the 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 information. Each transmission consists of a
start condition, an address byte, a command byte, and
finally a stop condition. The slave device acknowledges
the recognition of its address by pulling the SDA line
low for one clock period after the address byte is trans-
mitted. The slave device also issues a similar acknowl-
edgment after the command 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 bus master has fin-
ished communicating with the slave device, 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 MAX4584 uses an 8-bit-long slave address. To
select a slave address, connect A to V+ or GND. The
MAX4584 has two possible slave addresses, so a maxi-
mum of two of these devices may share the same
address line. The slave device MAX4584 monitors the
serial bus continuously, waiting for a start condition fol-
lowed by an address byte. When a slave device recog-
nizes its address (01101A10), it acknowledges that it is
ready for further communication by pulling the SDA line
low for one clock period.
MAX4584/MAX4585
Serially Controlled
Audio/Video Switches
_______________________________________________________________________________________ 9
Table 1. Command-Bit Mapping
Table 3. Address Bit Map
Table 2. Truth Table
X—XD4
X—XD5
X—XD6
X—XD7 (MSB)
POWER-UP
STATE
TERMINALSSWITCH
COMMAND
BIT
0 (Open)10, 1NO1A to COM1D0 (LSB)
1 (Closed)9, 1NO1B to COM1D1
0 (Open)6, 7NO2 to COM2D2
X—XD3
CLOSED1
OPEN0
NO1_ AND NO2LOGIC
0110 11101
0110 10100
ADDRESSADDRESS BIT (A)
