User Manual
Table Of Contents
- Document History
- Introduction
- Product Concept
- GSM Application Interface
- GSM/GPRS Operating Modes
- Power Supply
- Power Up / Down Scenarios
- Automatic GPRS Multislot Class Change
- Charging Control of the GSM Part
- Power Saving
- Summary of State Transitions (Except SLEEP Mode)
- RTC Backup for GSM Part of XT55/56
- Serial Interfaces of the XT55/56 GSM Part
- Audio Interfaces
- SIM Interface
- Control Signals
- GPS Application Interface
- GSM and GPS Antenna Interfaces
- Electrical, Reliability and Radio Characteristics
- Mechanics
- Reference Approval
- Example Applications
- List of Parts and Accessories
XT55/56 Hardware Interface Description
Confidential / Preliminary
s
XT55/56_hd_v02.96 Page 70 of 125 18.08.2005
1s
GSM_RING0
URC
3.12.3 Behavior of the GSM_RING0 Line (ASC0 Interface only)
The GSM_RING0 line is available on the first serial interface (ASC0). The signal serves to
indicate incoming calls and other types of URCs (Unsolicited Result Code).
Although not mandatory for use in a host application, it is strongly suggested that you
connect the GSM_RING0 line to an interrupt line of your application. In this case, the
application can be designed to receive an interrupt when a falling edge on GSM_RING0
occurs. This solution is most effective, particularly, for waking up an application from power
saving. Note that if the GSM_RING0 line is not wired, the application would be required to
permanently poll the data and status lines of the serial interface at the expense of a higher
current consumption. Therefore, utilizing the GSM_RING0 line provides an option to
significantly reduce the overall current consumption of your application.
The behavior of the GSM_RING0 line varies with the type of event:
• When a voice/fax/data call comes in the GSM_RING0 line goes low for 1s and high for
another 4s. Every 5 seconds the ring string is generated and sent over the GSM_RXD0
line.
If there is a call in progress and call waiting is activated for a connected handset or
handsfree device, the GSM_RING0 line switches to ground in order to generate acoustic
signals that indicate the waiting call.
Figure 24: Incoming voice call
• All other types of Unsolicited Result Codes (URCs) also
cause the GSM_RING0 line to go low, however for 1 second
only.
Figure 25: URC transmission
Table 19: ASC0 ring signal
Function Pin Status Description
0 Indicates an incoming call or URC. If in NON-CYCLIC
SLEEP mode CFUN=0 or CYCLIC SLEEP mode
CFUN=5 or 6, the module is caused to wake up to full
functionality. If CFUN=7 or 8, power saving is resumed
after URC transmission or end of call.
Ring indication GSM_RING0
1 No operation
4s
GSM_RING0
4s
1s
1s
1s
Ring
string
Ring
string
Ring
string