2.1.2.7
RI (Ring Indicator)
[Wireless CPU®
⇒
Host]
Output signal used as an alert from the Wireless CPU® to the Host to request
attention.
The Ring Indicator is used to inform the Host that the Wireless CPU® has something to
communicate. The RI could be activated for
•
an incoming voice call
•
an incoming circuit switched data call
•
an incoming packet switched data call
•
an incoming SMS
A falling edge on RI indicates incoming call or message. The signal remains low for a
period of time before going high. RI follows normal Ring Indication protocols,
generating a 1 second low pulse which is repeated until answered or disconnected by
the base-station, except for an incoming SMS, in which case there will only be one
low transition.
Note that an incoming call or SMS may also have an unsolicited
message associated with it. The RI will be used even when the Host
has RTS set to stop data from the Wireless CPU®.
NOTE
RI indicator is not essential for the sleep mode function. It is however a
complimentary means to alert the Host of an event which requires attention.
2.2
UART Logic
The UART1 signals described in this document are referenced to the GR/GS64 system
connector. The signal amplitudes are CMOS levels. A logic high (inactive state) signal
is at VREF (as defined in the Integrators Manual). VREF may differ, depending upon
which variant of the GR/GS64 family you are using. Please refer to the Integrators
Manual for details of digital IO and its operating limits as they apply to your
application and the variant product you are using.
2.3
Sleep Mode
In order to conserve current, the GR/GS64 Wireless CPU® (and sometimes the Host)
will benefit from transitioning to a low power state. The GSM standard permits a
feature known as DRX (Discontinuous Reception), a paging mode adopted by mobile
stations (the GR/GS64 device in this case) in which the radio transceiver is only
required to ‘awaken’ for network paging events on a relatively low duty-cycle basis.
APPLICATION NOTE
GR/GS64 UART Sleep Protocols
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