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
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XT55/56_hd_v02.96 Page 52 of 125 18.08.2005
activity. If the start bit of a received character is detected within these 9.2 ms, GSM_CTS will
be activated and the proper reception of the character will be guaranteed.
GSM_CTS will also be activated if any character is to be sent.
After the last character was sent or received the interface will remain active for
• another 2 seconds, if AT+CFUN=5 or 7,
• another 10 minutes, if AT+CFUN=6 or 8,
• or for an individual time defined with AT^SCFG, if AT+CFUN=9. Assertion of GSM_RTS
has the same effect.
In the pauses between listening to paging messages, while GSM_CTS is high, the module
resumes power saving and the AT interface is not accessible. See Figure 11 and Figure 12.
2.12 s
4.6 ms
4.6 ms
4.6 ms
4.6 ms
2.12 s
2.12 s
GS M _ CT S
AT interface disabled
AT interface enabled
Paging message Paging message Paging message
Paging message
4.6
ms
4.6
ms
4.6
ms
4.6
ms
Figure 11: Timing of CTS signal (example for a 2.12 s paging cycle)
Figure 12 illustrates the CFUN=5 and CFUN=7 modes, which reset the GSM_CTS signal 2
seconds after the last character was sent or received.
2.12 s
4.6 ms
2 s
4.6 ms
4.6 ms
2.12 s
2.12 s
AT interface disabled
AT interface enabled
1 character
st
Last character
Beginning of power saving
Paging message Paging message
Paging message
Paging message
4.6
ms
4.6
ms
GSM_CTS
Figure 12: Beginning of power saving if CFUN=5 or 7