Cinterion
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ELS31-VA/ELS51-VA Hardware Interface Description
3.3 Power Saving
76
ELS31-VA_ELS51-VA_HID_v01.000
2017-01-04
Confidential / Preliminary
Page 67 of 106
3.3.2
Wake-up via RTS0/RTS1
RTS0/RTS1 can be used to wake up ELS31-VA/ELS51-VA from SLEEP mode configured with
AT command. Assertion of either RTS0 or RTS1 (i.e., toggle from inactive high to active low)
serves as wake up event, thus allowing an external application to almost immediately terminate
power saving. After RTS0/RTS1 assertion, the CTS0/CTS1 line signals module wake up, i.e.,
readiness of the AT command interface. It is therefore recommended to enable RTS/CTS flow
control (default setting).
shows the described RTS0/RTS1 wake up mechanism.
•
RTS0/RTS1 must be high.
•
After a given programmable timeout (100ms up to 10s, default 5s) with no activity on ASC0
and ASC1 (and no data to transmit by module to host in Linux /dev/tty driver), CTS0/CTS1
will be driven high.
•
After a 2
nd
timeout (equal or greater than the duration needed to receive one character at
UART baudrate; ex: ~1.05ms for 10bit @ 9600baud), and while RTS0/RTS1 remains high
(which means an external application does not request the module to wake up), the module
will enter sleep mode.
•
Now, the host can wake-up the module driving RTS0/RTS1 from high to low.
•
Module will inform the host it is ready to receive over UART by driving CTS0/CTS1 to low.
Figure 36:
Wake-up via RTS0/RTS1
Note:
RTS0/RTS1 has to be high for ELS31-VA/ELS51-VA to be able to change into SLEEP
mode.
R T S 0 /R T S 1
C T S 0 /C T S 1
T X D 0 /T X D 1
R X D 0 /R X D 1
A T c o m m a n d
R e p ly
U R C
R T S a s s e r tio n ( f a llin g e d g e )
W a k e u p fr o m S L E E P m o d e
R e t u r n t o S L E E P
m o d e
R T S b a c k h ig h
< 1 .0 5 m s
1 0 0 m s
t o 1 0 s
1 0 0 m s
to 1 0 s
< 1 . 0 5 m s
S L E E P
m o d e
