DS2409
USAGE EXAMPLE
Configuration: A bus master controls a MicroLAN consisting of a trunk with many DS2409s that create
branches. Each of the DS2409s has a DS2430A connected to its auxiliary output to label its physical
location in the network (see Figure 10). iButton devices are constantly arriving at or departing from the
branches.
Task: Identify one branch where an iButton has arrived and get the branch’s physical location. Determine
the population on that particular branch.
STEP MASTER MODE
DATA (LSB FIRST)
COMMENTS
Reset pulse (480–960 µs)
Presence pulse
1
2
TX
RX
Reset
Presence
ECh
3
TX
Issue “conditional search ROM” command
4
5
6
RX/RX/TX
TX
for each of the 64 ROM bits Identify and access one of the qualifying devices
33h
FFh
Issue Smart-On Auxiliary command
Send reset stimulus
TX
7
8
RX
RX
<data byte>*
33h
Get reset response byte with presence info
Get confirmation byte
9
TX
TX
RX
TX
RX
TX
TX
TX
TX
RX
RX
TX
CCh
F0h
<32 data bytes>
Reset
Presence
55h
<8 byte ROM ID>
CCh
Issue “skip ROM” command
Issue “read memory” command
Get branch location information (DS2430A)
Reset pulse
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
Presence pulse
Issue “Match ROM” command
Access the previously identified coupler
Issue Smart-On Main command
Send reset stimulus
Get reset response byte with presence info
Get confirmation byte
FFh
<data byte>*
CCh
F0h
Issue “search ROM” command
RX/RX/TX
TX
for each of the 64 ROM bits Identify one of the devices connected
Reset
Presence
55h
Reset pulse
Presence pulse
RX
TX
TX
TX
RX
TX
RX
Issue “Match ROM” command
Access the previously identified coupler
Send all lines off command
Get confirmation byte
Reset pulse
<8 byte ROM ID>
66h
66h
Reset
Presence
Presence pulse
repeat steps 12 to 21 for each of the remaining devices on the branch of the identified coupler
* 00h or 01h if presence pulse, FFh if no presence pulse
Note: The sequence of steps 12 to 21 logically decouples all other devices residing on the trunk from
responding to the search ROM command. The All Lines Off command is required to clear the event flag
that made the device respond to the conditional search command.
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