User's Manual

XT55/56 Hardware Interface Description
Confidential / Released
s
XT55/56_hd_v02.06a Page 50 of 125 17.12.2004
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 10 and Figure 11.
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 10: Timing of CTS signal (example for a 2.12 s paging cycle)
Figure 11 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 11: Beginning of power saving if CFUN=5 or 7