TOBY-L2 and MPCI-L2 series - System Integration Manual
UBX-13004618 - R07
Advance Information
System description
Page 46 of 158
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 interface (for more details see
section 1.9.2.4 and in particular Figure 22).
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. For more details, 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
[3], 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 interface, as described in Figure 22.
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
1.9.2.4 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
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
hardware flow control status can be configured by AT commands
(for more details, see the
u-blox AT Commands Manual
[3], AT&K, AT\Q, AT+IFC AT commands).
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 1.9.2.4 and
u-blox AT Commands Manual
[3], 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 ~5 ms from the transition the switch is completed and data can be received without loss.
The module cannot enter low power idle-mode and the UART is keep enabled as long as the
RTS
input line
is held 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
