User's Manual

LISA-U1/LISA-H1 series - System Integration Manual
3G.G2-HW-10002-2 Advance Information System description
Page 45 of 116
TxD signal behavior
The module data input line (TxD) is set by default to OFF state (high level) at UART initialization. The TxD line is
then held by the module in the OFF state if the line is not activated by the DTE: an active pull-up is enabled
inside the module on the TxD input.
CTS signal behavior
The module hardware flow control output (CTS line) is set to the ON state (low level) at UART initialization.
If the hardware flow control is enabled (for more details please refer to u-blox AT Commands Manual [2], AT&K,
AT\Q, AT+IFC AT command) the CTS line indicates when the UART interface is enabled (data can be sent and
received): the module drives the CTS line to the ON state or to the OFF state when it is either able or not able to
accept data from the DTE (refer to chapter 1.9.2.3 for the complete description).
If the hardware flow control is not enabled, the CTS line is always held in the ON state after UART initialization.
In case of hardware flow control enabled, when CTS line is ON the UART is enabled and the module is
in active mode. Instead, CTS line to OFF doesn’t necessary mean that the module is in idle-mode, but
only that the UART is not enabled (the module could be forced to stay in active-mode for instance by
USB).
When the power saving configuration is enabled and the hardware flow-control is not implemented in
the DTE/DCE connection, data sent by the DTE can be lost: the first character sent when the module is in
idle-mode won’t be a valid communication character (refer to chapter 1.9.2.3 for the complete
description).
During the MUX mode, the CTS line state is mapped to FCon / FCoff MUX command for flow control
issues outside the power saving configuration while the physical CTS line is still used as a power state
indicator. For more details please refer to Mux Implementation Application Note [15].
RTS signal behavior
The hardware flow control input (RTS line) is set by default to the OFF state (high level) at UART initialization.
The RTS line is then held by the module in the OFF state if the line is not activated by the DTE: an active pull-up
is enabled inside the module on the RTS input.
If the HW flow control is enabled (for more details please refer to u-blox AT Commands Manual [2] AT&K, AT\Q,
AT+IFC command description) the RTS line is monitored by the module to detect permission from the DTE to
send data to the DTE itself. If the RTS line is set to OFF state, any on-going data transmission from the module is
immediately interrupted or any subsequent transmission forbidden until the RTS line changes to ON state.
The DTE must be able to still accept a certain number of characters after the RTS line has been set to
OFF state: the module guarantees the transmission interruption within 2 characters from RTS state
change.
If AT+UPSV=2 is set and HW flow control is disabled, the RTS line is monitored by the module to manage the
power saving configuration:
 When an OFF-to-ON transition occurs on the RTS input line, the UART is enabled and the module is forced
to active-mode; after 20 ms from the transition the switch is completed and data can be received without
loss. The module can’t enter idle-mode and the UART is keep enabled as long as the RTS input line is held in
the ON state
 If RTS is set to OFF state by the DTE, the module automatically enters idle-mode whenever possible as in the
AT+UPSV=1 configuration (cyclic idle/active mode), but UART is disabled (held in low power mode)
For more details please refer to chapter 1.9.2.3 and u-blox AT Commands Manual [2], AT+UPSV command.