Behaviors Of The Ring Line (The Main Serial Interface Only) - SimCom SIM802 HD Manual

SIM802 Hardware Design

3.15 Behaviors of the Ring line (The main serial interface only)

Table 23: Behaviours of the Ring line
State RI respond
Standby HIGH
Voice calling Change LOW, then:
（ 1 ） Change to HIGH when establish calling.
（ 2 ） Use AT command ATH, the RI Pin changes to HIGH.
（ 3 ） Sender hangs up, change to HIGH.
(4) Change to HIGH when SMS received.
Data calling Change LOW, then ：
（ 1 ） Change to HIGH when establish calling.
（ 2 ） Use AT command ATH, the RI changes to HIGH.
SMS When receive SMS, The RI will change to LOW and hold low level about
120 ms, then change to HIGH.
URC Some URCs triggers 120ms low level on RI. For more details, please refer
to document[10]
If the module is used as caller, signal RI will maintain high. But when it is used as receiver,
following is timing of RI.
RI
HIGH
LOW
Power on
SIM802_HD_V2.01
Ring
Ring
MO or MT
Hang up
Figure 30: SIM802 Services as Receiver
Figure 31: SIM802 Services as caller
Hang on
MO or
(talking) MT
Hang up
56
Ring
12.01.2010