DS2413: 1-Wire Dual Channel Addressable Switch

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The idle state for the 1-Wire bus is high. If for any reason a transaction needs to be suspended, the bus MUST be

left in the idle state if the transaction is to resume. If this does not occur and the bus is left low for more than 16µs

(Overdrive speed) or more than 120µs (standard speed), one or more devices on the bus may be reset.

Figure 9. Hardware Configuration

Open Drain

Port Pin

RX = RECEIVE

TX = TRANSMIT

100

Ω

MOSFET

RX

TX

TX

RX

DATA

BUS MASTER

DS2413 1-Wire PORT

TRANSACTION SEQUENCE

The protocol for accessing the DS2413 through the 1-Wire port is as follows:

Initialization

ROM Function Command

PIO Function Command

Data

INITIALIZATION

All transactions on the 1-Wire bus begin with an initialization sequence. The initialization sequence consists of a

reset pulse transmitted by the bus master followed by presence pulse(s) transmitted by the slave(s). The presence

pulse lets the bus master know that the DS2413 is on the bus and is ready to operate. For more details, see the 1-

Wire Signaling section.

1-Wire ROM FUNCTION COMMANDS

Once the bus master has detected a presence, it can issue one of the seven ROM function commands that the

DS2413 supports. All ROM function commands are 8 bits long. A list of these commands follows (refer to the flow

chart in Figure 10).

READ ROM [33h]

This command allows the bus master to read the DS2413’s 8-bit family code, unique 48-bit serial number, and 8-bit

CRC. This command can only be used if there is a single slave on the bus. If more than one slave is present on the

bus, a data collision occurs when all slaves try to transmit at the same time (open drain produces a wired-AND

result). The resultant family code and 48-bit serial number result in a mismatch of the CRC.

MATCH ROM [55h]

The Match ROM command, followed by a 64-bit ROM sequence, allows the bus master to address a specific

DS2413 on a multidrop bus. Only the DS2413 that exactly matches the 64-bit ROM sequence, including the

external address, responds to the following PIO Function command. All other slaves wait for a reset pulse. This

command can be used with a single or multiple devices on the bus.