NB-IoT Module Series
BC95 Hardware Design
BC95_Hardware_Design Confidential / Released 22 / 51
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T3324
T3412
TAU
UE inactive time
Idle
Figure 8: Diagram for Power Consumption
The procedure for entering PSM is as follows: the module requests to enter PSM in “ATTACH REQUEST”
message during attach/TAU (Tracking Area Update) procedure. Then the network accepts the request
and provides an active time value (T3324) to the module and the mobile reachable timer starts. When the
T3324 timer expires, the module enters PSM for duration of T3412 (periodic TAU timer). Please note that
the module cannot request PSM when it is establishing an emergency attachment or initializing the PDN
(Public Data Network) connection.
When the module is in PSM, it cannot be paged and stops access stratum activities such as cell
reselection, and T3412 is still active.
When MO (Mobile Originated) data are sent or the periodic TAU timer expires, the module will exit from
PSM.
3.8. UART Interfaces
The module provides two UART ports: main port and debug port. The module is designed as DCE (Data
Communication Equipment), following the traditional DCE-DTE (Data Terminal Equipment) connection.
The main port:
TXD: Send data to RXD of DTE.
RXD: Receive data from TXD of DTE.
RI*: Ring indicator (when an SMS message is received or data is transmitted, the module will output
signals to inform DTE).
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