Wavenet Technology Pty Ltd. BM3900M Manuel D’Utilisation

Boomer-III User Manual & Integrator’s Guide_________________________________________________Installation 

 

BM310012WT05 

35 

Copyright Wavenet Technology © October 2003 

LED Output Lines 
In addition to the on-board LED’s there are three signal lines (Low 
Battery, Message Waiting, In-range), which are controllable by the 
modem for connection to an external LED. These lines also have multi-
function capability through software configuration as digital 
input/outputs or as a Synchronous Peripheral Interface (SPI) port. SS4 
may be used as a SPI chip select signal (refer to Status Signals section 
previously). 
Each LED output line has a 33Ω series resistor for protection. It is 
recommended a series resistor be used with the external LED to limit 
current accordingly. The electrical interface capability, equivalent 
circuit and operation of these lines is summarized in the tables below: 

13 

LED0_MSGWTG 

LED Signal 0 

Input/ Output 

SPI_CLK 

14 

LED1_INRANGE 

LED Signal 1 

Input/ Output 

SPI_MOSI 

15 

LED2_LOWBAT 

LED Signal 2 

Input/ Output 

SPI_MISO 

 

 
 
 
 
 
 
 

Output Voltage 

0 – 3V 

0.4 V (max) 

2.5 V (min) 

Output Current 

 

4 mA (max) 

4 mA (min)