Echelon FT 3150 Smart Transceiver - Manual (Page 33)

FT 3120 / FT 3150 Smart Transceiver Data Book 27
Additional Functions
SERVICE Pin
The SERVICE pin alternates between input and open-drain output at a 76 Hz rate with a 50% duty cycle. When it is
an output, it can sink 20 mA for use in driving a LED. When it is used exclusively as an input, it has an optional on-
chip pull-up to bring the input to an inactive-high state for use when the LED and pull-up resistor are not connected.
Under control of the Neuron firmware, this pin is used during configuration, installation, and maintenance of the
device containing the FT Smart Transceiver. The firmware flashes the LED at a 1/2-Hz rate when the FT Smart
Transceiver has not been configured with network address information. Grounding the SERVICE pin causes the FT
Smart Transceiver to transmit a network management message containing its unique 48-bit Neuron ID and the
program ID of the application on the network. This information may then be used by a network tool to install and
configure the device. A typical circuit for the SERVICE pin LED and push-button is shown in Figure 2.12. During
reset the SERVICE pin state is indeterminate. The default state of the SERVICE pin pull-up is enabled.
Figure 2.12 FT Smart Transceiver SERVICE Pin Circuit
V
SS
Drive Out
SERVICE Pin
Signal Out
Firmware
Samples
For driving a 50% duty cycle output.
Waveform is sampled for external ground condition.
20 mA
Sink
Broadcast
ID
Config
Pull-Up
LED
SERVICE
V
DD
Three-
State
Low Low Low
Three-
State
Three-
State
FT 3120/3150 Smart Transceiver