NINA-W1 series - User Manual
CTS is an input to the NINA-W1 module and if the host applies a 0 (ON state = low level), then the
module is allowed to transmit.
RTS is an output off the NINA-W1 module and the module will apply a 0 (ON state = low level)
when it is ready to receive transmission.
3.4.2
Ethernet (RMII+SMI)
It is recommended to route all signals in the RMII bus with the same length and have appropriate
grounding in the surrounding layers; total bus length should also be minimized. The layout of the
RMII bus should be done so that crosstalk with other parts of the circuit is minimized providing
adequate isolation between the signals, the clock and the surrounding busses/traces.
Termination resistors are recommended for the RX and TX lines on the RMII bus.
Pull-up resistor is required for MDIO.
The General High Speed layout guidelines in section 3.5 apply for the RMII and the SMI bus.
3.5
General High Speed layout guidelines
These general design guidelines are considered as best practices and are valid for any bus present in
the NINA-W1 series modules; the designer should prioritize the layout of higher speed busses. Low
frequency signals are generally not critical for layout.
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One exception is represented by High Impedance traces (such as signals driven by weak pull
resistors) that may be affected by crosstalk. For those traces, a supplementary isolation of 4w
from other busses is recommended.
3.5.1
General considerations for schematic design and PCB floor-planning
Verify which signal bus requires termination and add series resistor terminations to the
schematics.
Carefully consider the placement of the module with respect to antenna position and host
processor.
Verify with PCB manufacturer allowable stack-ups and controlled impedance dimensioning.
Verify that the power supply design and power sequence are compliant with the specification of
NINA-W1 series module.
3.5.2
Module placement
Accessory parts like bypass capacitors should be placed as close as possible to the module to
improve filtering capability, prioritizing the placement of the smallest size capacitor close to
module pads.
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Particular care should be taken not to place components close to the antenna area. The designer
should carefully follow the recommendations from the antenna manufacturer about the distance
of the antenna vs. other parts of the system. The designer should also maximize the distance of
the antenna to Hi-frequency busses like DDRs and related components or consider an optional
metal shield to reduce interferences that could be picked up by the antenna thus reducing the
module’s sensitivity.
An optimized module placement allows better RF performance. See section 3.3 for more
information on antenna consideration during module placement.
3.5.3
Layout and manufacturing
Avoid stubs on high speed signals. Even through-hole vias may have an impact on signal quality.
