DS2480B

In addition to the command codes explained in the subsequent sections the DS2480B understands the

following reserved command codes:

E1h

switch to Data Mode

E3h

switch to Command Mode

F1h

pulse termination

Except for these reserved commands, the Search Accelerator control and the first byte after power-on

reset or master reset cycle, every legal command byte generates a response byte. The pulse termination

code triggers the response byte of the terminated pulse command. Illegal command bytes do not generate

a command response byte.

COMMUNICATION COMMANDS

The DS2480B supports four communication function commands: Reset, Single Bit, Pulse, and Search

Accelerator control. Details on the assignment of each bit of the command codes are shown in Table 1.

The corresponding command response bytes are detailed in Table 2. The Reset, Search Accelerator

Control and Single Bit commands include bits to select the 1-Wire communication speed (standard,

flexible, Overdrive). Even if a command does not generate activity on the 1-Wire bus, these bits are

latched inside the device and will take effect immediately.

Reset

The Reset command must be used to begin all 1-Wire communication. The speed selection included in

the command code immediately takes effect. The response byte includes a code for the reaction on the

1-Wire bus (bits 0 and 1) and a code for the chip revision (bits 2 to 4).

Single Bit

The Single Bit command is used to generate a single time slot on the 1-Wire bus at the speed indicated by

bits 2 and 3. The type of the time slot (Write-0 or Write-1) is determined by the logic value of bit 4. A

Read Data time slot is identical to the Write-1 time slot. Bits 0 and 1 of the response byte transmitted by

the DS2480B at the end of the time slot reveal the value found on the 1-Wire bus when reading.

For a time slot without a subsequent strong pullup, bit 1 of the command must be set to 0. For a time slot

immediately followed by a strong pullup bit 1 must be set to 1. As soon as the strong pullup is over, the

device will send a second response byte, code EFh (read 1) or ECh (read 0), depending on the value

found on the 1-Wire bus when reading.

Maxim Integrated ............................................................................................................................................................................................. 6