TOBY-L2 and MPCI-L2 series - System Integration Manual
UBX-13004618 - R28
System description
Page 46 of 164
CTS signal behavior
The module HW 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 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 (for example
see section
☞
The module guarantees the reception of characters when the CTS line is set to the ON state, and
the module is also able to accept up to 3 characters after the CTS line is set to the OFF state.
☞
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.
☞
If hardware flow control is enabled and the multiplexer protocol is active, then the CTS line state
is mapped to Fcon / Fcoff MUX command for flow control matters outside the power saving
configuration while the physical CTS line is still used as a UART power state indicator (see the Mux
Implementation Application Note
The CTS hardware flow control setting can be changed by AT commands (for more details, see the
u-blox AT Commands Manual
, AT&K, AT\Q, AT+IFC AT commands).
If the hardware flow control is not enabled, the CTS line still indicates when the UART interface is
enabled, as it does when hardware flow control is enabled. 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.
☞
When the power saving configuration is enabled by 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
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 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.
The module behavior according to the RTS HW flow control status can be configured by AT
commands (for more details, see the u-blox AT Commands Manual
, AT&K, AT\Q, AT+IFC AT
commands).
