DS2409 Dallas Semiconducotr, DS2409 Datasheet - Page 15

• Manufacturer Part Number: DS2409
• Description: MicroLAN Coupler
• Manufacturer: Dallas Semiconducotr

DS2409
APPLICATION EXAMPLES
Figures 10 and 11 show two application examples of the DS2409 MicroLAN Coupler. A single trunk
with branches is the typical topology of an access control system with the iButtons being the electronic
keys required for admittance. The host computer runs a program that scans the devices on the trunk for
events (conditional search). When somebody touches the probe with an iButton, this will set the event
flag of the main line and the coupler will respond. The ID chip represents the DS2430A that labels the
access point. The 64-bit ROM ID of the arriving iButton is the key for the entrance. In a real access
control application, the LED will be replaced by a solenoid that opens the lock under software control
(manual mode). The same network topology could be used for an inventory control system with the
branches representing individual shelves of a rack. The iButtons would be electronic tags mounted on
objects sitting on the shelves. The LED would guide the warehouse worker in placing the objects onto the
right shelf.
The dual-master system realizes a master to master communication path via the 1-Wire bus. The DS1996
Memory iButton serves as a temporary storage for the data packets to be exchanged. When idle, both
main outputs as well as the auxiliary outputs are inactive. To access the Memory iButton, the host A first
switches on the control output, thereby pulling the auxiliary line of the coupler at the B side low. This
tells host B that it is not allowed to activate the main output of coupler B. Now host A activates the main
output of coupler A and writes data to the Memory iButton. After the writing is complete, host A
deactivates the main output of coupler A and switches off the control output. Host B meanwhile has been
polling the logic level at the auxiliary line of coupler B and realizes that host A has finished the access.
Now host B follows the same procedure and accesses the memory to read the data, etc. The memory
iButton may be replaced by a MicroLAN network. The Silicon Label stores information telling the hosts
that these particular couplers access the same network and that the control and auxiliary outputs are cross-
coupled for handshaking.
MicroLAN TRUNK WITH BRANCHES Figure 10
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