Gemalto M2M GmbH MC56 User Manual

MC55/56 Hardware Interface Description 
Confidential / Preliminary 

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MC55/56_hd_v03.00 

Page 63 of 104 

16.08.2005 

As an alternative to generating the synchronization signal, the SYNC pin can be used to 
control a status LED on your application platform.  
 
Especially in the development and test phase of an application, system integrators are 
advised to use the LED mode of the SYNC pin in order to evaluate their product design and 
identify the source of errors. 
 
To avail of this feature you need to set the SYNC pin to mode 1 by using the AT^SSYNC 
command. For details see [1].  
 

Table 18: Coding of the status LED 

Permanently off 

MC55/56 is in one of the following modes:  
•  POWER DOWN mode 
• ALARM 

mode 

• CHARGE-ONLY 

mode 

•  NON-CYCLIC SLEEP mode 
•  CYCLIC SLEEP mode with no temporary wake-up event in 

progress. 

600 ms on / 600 ms off 

Limited Network Service: No SIM card inserted or no PIN entered, or 
network search in progress, or ongoing user authentication, or network 
login in progress. 

75 ms on / 3 s off 

IDLE mode: The mobile is logged to the network (monitoring control 
channels and user interactions). No call in progress. 

75 ms on / 75 ms off /  
75 ms on / 3 s off 

One or more GPRS contexts activated. 

0.5 s on / off depending on 
transmission activity  

Packet switched data transfer in progress. LED goes on within 
1 second after data packets were exchanged. Flash duration is 
approximately 0.5 s.  

75 ms 

URC 

Permanently on 

Depending on type of call: 
Voice call: Connected to remote party. 
CSD call: Connected to remote party or exchange of parameters while 
setting up or disconnecting a call. 
 

LED Off = SYNC pin low. LED On = SYNC pin high (if LED is connected as illustrated in Figure 23) 

 
Note:   When a temporary wake-up event (URC, call, packet switched transfer) occurs in 

CYCLIC SLEEP mode the LED flashes. See Table 11 for details on the various 
SLEEP modes and wake-up events.