DS28E16 datasheet(13/15 Pages) MAXIM

13 / 15 page

Search ROM[F0h]

When a system is initially brought up, the bus master

might not know the number of devices on the 1-Wire bus

or their ROM ID numbers. By taking advantage of the

wired-AND property of the bus, the master can use a pro-

cess of elimination to identify the ID of all slave devices.

For each bit in the ID number, starting with the least sig-

nificant bit, the bus master issues a triplet of time slots.

On the first slot, each slave device participating in the

search outputs the true value of its ID number bit. On the

second slot, each slave device participating in the search

outputs the complemented value of its ID number bit. On

the third slot, the master writes the true value of the bit

to be selected. All slave devices that do not match the

bit written by the master stop participating in the search.

If both of the read bits are zero, the master knows that

slave devices exist with both states of the bit. By choos-

ing which state to write, the bus master branches in the

search tree. After one complete pass, the bus master

knows the ROM ID number of a single device. Additional

passes identify the ID numbers of the remaining devices.

Refer to Application Note 187: 1-Wire Search Algorithm

for a detailed discussion, including an example.

Read ROM[33h]

The Read ROM command allows the bus master to read

the DS28E16’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

DS28E16 on a multidrop bus. Only the DS28E16 that

exactly matches the 64-bit ROM sequence responds

to the subsequent device function command. All other

slaves wait for a reset pulse. This command can be used

with a single device or multiple devices on the bus.

Skip ROM [CCh]

This command can save time in a single-drop bus system

by allowing the bus master to access the device functions

without providing the 64-bit ROM ID. If more than one

slave is present on the bus and, for example, a read com-

mand is issued following the Skip ROM command, data

collision occurs on the bus as multiple slaves transmit

simultaneously (open-drain pulldowns produce a wired-

AND result).

Resume [A5h]

To maximize the data throughput in a multidrop environ-

ment, the Resume command is available. This com-

mand checks the status of the RC bit and, if it is set,

directly transfers control to the device function com-

mands, similar to a Skip ROM command. The only way

to set the RC bit is through successfully executing the

Match ROM or Search ROM command. Once the RC bit

is set, the device can repeatedly be accessed through

the Resume command. Accessing another device on

the bus clears the RC bit, preventing two or more

devices from simultaneously responding to the Resume

command.

www.maximintegrated.com

Maxim Integrated │ 13

DS28E16

1-Wire Secure SHA-3 Authenticator

DS28E16 Datasheet(PDF) 13 Page - Maxim Integrated Products

DS28E16 Datasheet(HTML) 13 Page - Maxim Integrated Products

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Datasheet Download

Link URL