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LARA-R2 series - System Integration Manual

UBX-16010573 - R12

System description

Page 41 of 157

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, as it is by default, 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 over the UART (see 1.9.1.4 for more details).

If hardware flow control is enabled, then when the

CTS

line is OFF it does not necessarily mean that the

module is in low power idle mode, but only that the UART is not enabled, as the module could be forced
to stay in active mode for other activities, e.g. related to the network or related to other interfaces.

When the multiplexer protocol is active, 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, see

Mux Implementation Application Note

[21].

The

CTS

hardware flow control setting can be changed by using AT commands (for more details, see the

u-blox

AT Commands Manual

[2], AT&K, AT\Q, AT+IFC, AT+UCTS AT command).

When the power saving configuration is enabled by the AT+UPSV command 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 low power idle mode will not be a valid communication character (see section 1.9.1.4
and in particular the sub-section “Wake-up via data reception” for further details).

RTS signal behavior

The hardware flow control input (

RTS

line) is set by default to the OFF state (high level) at UART initialization. The

module then holds the

RTS

line 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, as it is by default, the module monitors the

RTS

line to detect permission from

the DTE to send data to the DTE itself. If the

RTS

line is set to the OFF state, any on-going data transmission from

the module is interrupted until the subsequent

RTS

line changes to the ON state.

The DTE must still be able to accept a certain number of characters after the

RTS

line is set to the OFF state:

the module guarantees the transmission interruption within two characters from

RTS

state change.

Module behavior according to

RTS

hardware flow control status can be configured by using AT commands (for

more details, see the

u-blox AT Commands Manual

[2], AT&K, AT\Q, AT+IFC command descriptions).

If AT+UPSV=2 is set and HW flow control is disabled, the module monitors the

RTS

line to manage the power

saving configuration (for more details, see section 1.9.1.4 and the

u-blox AT Commands Manual

[2], AT+UPSV):



When an OFF-to-ON transition occurs on the

RTS

input, the UART is enabled and the module is forced to

active mode. After ~20 ms, the switch is completed and data can be received without loss. The module cannot
enter low power idle mode and the UART is enabled as long as the

RTS

is in the ON state.



If the

RTS

input line is set to the OFF state by the DTE, the UART is disabled (held in low power mode) and the

module automatically enters low power idle mode whenever possible.

DSR signal behavior

If AT&S1 is set, as it is by default, the

DSR

module output line is set by default to the OFF state (high level) at UART

initialization. The