LEON-G100 / LEON-G200 - System Integration Manual
GSM.G1-HW-09002-G3
Preliminary
System description
Page 50 of 125
Wake up from idle-mode to active-mode via data reception
If a data is transmitted by the DTE during the module idle-mode, it will be lost (not correctly received by the
module) in the following cases:
AT+UPSV=1 with hardware flow control disabled
AT+UPSV=2 with hardware flow control disabled and RTS line set to OFF
When the module is in idle-mode, the
TxD
input line of the module is always configured to wake up the module
from idle-mode to active-mode via data reception: when a low-to-high transition occurs on the
TxD
input line, it
causes the wake-up of the system. The module switches from idle-mode to active-mode after 20 ms from the
first data reception: this is the “wake up time” of the module. As a consequence, the first character sent when
the module is in idle-mode (i.e. the wake up character) won’t be a valid communication character because it
can’t be recognized, and the recognition of the subsequent characters is guaranteed only after the complete
wake-up (i.e. after 20 ms).
Figure 29 and Figure 30 show an example of common scenarios and timing constraints:
HW flow control set in the DCE, and no HW flow control set in the DTE, needed to see the
CTS
line
changing on DCE
Power saving configuration is active and the timeout from last data received to idle-mode start is set to 2000
frames (AT+UPSV=1,2000)
Figure 29 shows the case where DCE is in idle mode and a wake-up is forced. In this scenario the only character
sent by the DTE is the wake-up character; as a consequence, the DCE will return to idle-mode when the timeout
from last data received expires. (2000 frames without data reception).
CTS OFF
CTS ON
Active mode is held for 2000 GSM frames (~9.2 s)
time
Wake up time: up to 15.6 ms
time
TxD
module
input
Wake up character
Not recognized by DCE
Figure 29: Wake-up via data reception without further communication
