Cinterion
®
ELS31-VA/ELS51-VA Hardware Interface Description
2.1 Application Interface
56
ELS31-VA_ELS51-VA_HID_v01.000
2017-01-04
Confidential / Preliminary
Page 43 of 106
2.1.16.2
Power Indication Circuit
In Power Down mode the maximum voltage at any digital or analog interface line must not ex-
ceed +0.3V (see also
). Exceeding this limit for any length of time might cause
permanent damage to the module.
It is therefore recommended to implement a power indication signal that reports the module’s
power state and shows whether it is active or in Power Down mode. While the module is in
Power Down mode all signals with a high level from an external application need to be set to
low state or high impedance state. The sample power indication circuit illustrated in
denotes the module’s active state with a low signal and the module’s Power Down mode with
a high signal or high impedance state.
Figure 19:
Power indication circuit
2.1.16.3
Host Wakeup
If no call, data or message transfer is in progress, the host may shut down its own USB inter-
face to save power. If a call or other request (URC’s, messages) arrives, the host can be noti-
fied of these events and be woken up again by a state transition of the ASC0 interface‘s RING0
line. This functionality should only be used with legacy USB applications not supporting the rec-
ommended USB suspend and resume mechanism as described in
For more information on how to configure the RING0 line by AT^SCFG command see
.
Possible RING0 line states are listed in
Table 11:
Host wakeup line
Signal
I/O
Description
RING0
O
Inactive to active low transition:
0 = The host shall wake up
1 = No wake up request
22k
10
k
10
0
k
10
0
k
4.7k
V180
VCORE
Power
indication
External
power supply
