DS1996

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for more than 16 µs (Overdrive Speed) or more than 120 µs (regular speed), one or more of the devices

on the bus may be reset.

HARDWARE CONFIGURATION Figure 8

TRANSACTION SEQUENCE

The protocol for accessing the DS1996 via the 1-Wire port is as follows:

§ Initialization

§ ROM Function Command

§ Memory Function Command

§ Transaction/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 DS1996 is on the bus and is ready to operate. For

more details, see the ”1-Wire Signaling” section.

ROM FUNCTION COMMANDS

Once the bus master has detected a presence, it can issue one of the six ROM function commands. All

ROM function commands are eight bits long. A list of these commands follows (refer to flowchart in

Figure 9).

Read ROM [33H]

This command allows the bus master to read the DS1996’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 DS1996 on the bus. If more

than one slave is present on the bus, a data collision will occur when all slaves try to transmit at the same

time (open drain will produce a wired-AND result). The resultant family code and 48-bit serial number

will usually result in a mismatch of the CRC.