User's Manual
PCS3_HD_v01.000-03
Confidential / Preliminary
Page 49 of 101
2013-10-21
PCS3 Hardware Interface Description
3.10 Control Signals
3.10.3
Behavior of the RING0 Line (ASC0 Interface only)
The RING0 line is available on the first serial interface ASC0 (see also Section 3.7). 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 RING0 line to an interrupt line of your application. In this case, the application can be de-
signed to receive an interrupt when a falling edge on RING0 occurs. This solution is most ef-
fective, particularly, for waking up an application from power saving. Note that if the 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
RING0 line provides an option to significantly reduce the overall current consumption of your
application.
The RING0 line behavior and usage can be configured by AT command. For details see [1]:
AT^SCFG.
3.10.4
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) arrives, the host can be notified of this event
and be woken up again by a state transition of either the RING0 or the WAKEUP line. This func-
tionality should only be used with legacy USB applications not supporting the recommended
USB suspend and resume mechanism as described in in the “Universal Serial Bus Specifica-
tion Revision 2.0“
1
(see also Section 3.6.1).
The behaviour of these RING0 or WAKEUP lines as host wakeup line has to be enabled and
configured by AT command (see [1]: AT^SCFG). Possible states are listed in Table 14. Please
note that it is not possible to use both lines in parallel. The WAKEUP signal just inverts the
RING0 signal in order to meet different application needs.
Table 14: Host wakeup lines
Signal I/O Description
RING0 O
Inactive to active low transition:
0 = The host shall wake up
1 = No wake up request
WAKEUP O
Inactive to active high transition:
0 = No wake up request
1 = The host shall wake up
1.
The specification is ready for download on http://www.usb.org/developers/docs/