Embedded Planet CHRONOS User Manual page 9

Pin # Pin Name Pin Type
13 PWR_MON Digital output
14 Vcell_ref Power input
15 GND n/a
16 RTS Digital input
17 TX_AUX Digital output
18 RX_AUX Digital input
19 RING Digital output
20 ON_OFF# Open
collector
input
Note: In some use cases, ON_OFF# can be tied to GND.
If this is done, there are two items to consider:
1. PSM asynchronous wake-up capability will be lost.
2. To perform an unconditional shutdown in this configuration, it is necessary to send
AT#SHDN and then turn off Vcell.
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Description
Cell module power monitor
Reference voltage for host
GPIO
GND
Main UART RTS input to cell
module
Aux UART output from cell
module
Aux UART input to cell
module
Output from cell module
indicating incoming call
Input command for power
ON/OFF and to wake from
deep sleep mode
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User Manual | Chronos
If not used
Leave open
Leave open
Must be
implemented
Leave open
Leave open
Leave open
Leave open
Tie to GND
(see note
below)
Notes
High when
cell module is
ON
If not used as
RING, this pin
can be used
as a GPIO
Active Low
page 8