Specifications

MC55/56 Hardware Interface Description

Confidential / Released

MC55/56_hd_v04.00a Page 65 of 108 24.08.2006

3.12.2.2 Using the SYNC pin to control a status LED

As an alternative to generating the synchronization signal, the SYNC pin can be used to

drive a status LED on your application platform. To avail of this feature you need to set

AT^SSYNC=1. For details see

[1].

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.

During the transition from one LED pattern to another the "on" and/or "off" periods of the

LED may vary in length. This is because an event that triggers the change may occur any

time and, thus, truncate the current LED pattern at any point.

States of the SYNC pin (if AT^SSYNC=1 and LED connected as illustrated in

Figure 23):

LED Off = SYNC pin low. LED On = SYNC pin high

Table 18: Coding of the status LED

LED mode Operating status of MC55/56

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

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

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.

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.

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

SLEEP mode the LED flashes according to the patterns listed above. See Table 11 for details on the

various SLEEP modes and wake-up events.