MRF24WB0MA Datasheet, PDF (16/34 Pages) Microchip Technology – 2.4 GHz, IEEE Std. 802.11b™ RF Transceiver Module

MRF24WB0MA/MRF24WB0MB
2.6 SPI Interface
The slave Serial Peripheral Interface (SPI) is used to
interface with the host PIC microcontroller. The slave
SPI interface works with the Interrupt line (INT). When
data is available for the PIC microcontroller during
operation, the INT line is asserted low by the
MRF24WB0MA/MRF24WB0MB module. The INT line
is de-asserted high by the MRF24WB0MA/
MRF24WB0MB after the data is transferred to the host
PIC microcontroller. The SPI SCK speed can be up to
25 MHz.
The slave SPI interface implements the [CPOL=0;
CPHA=0] and [CPOL=0; CPHA=1] modes (0 and 3) of
operation. That is, data is clocked in on the first rising
edge of the clock after Chip Select (CS) is asserted.
Data is placed on the bus with most significant bit
(MSb) first and least significant bit (LSb) last.
Figure 4-1 in Section 4.0 “Electrical Characteris-
tics” shows the SPI timing diagram. Table 4-7 details
the SPI timing AC characteristics.
2.7 PCB Antenna
The PCB antenna is fabricated on the top copper layer
and covered in solder mask. The layers below the
antenna have no copper trace.
It is recommended that the module be mounted on the
edge of the host PCB. It is permitted for PCB material
to be below the antenna structure of the module as long
as no copper traces or planes are on the host PCB in
that area. For best performance, place the module on
the host PCB according to the details shown in
Figure 1-4.
The antenna patterns shown in the following plots, des-
ignated as Figure 2-4, Figure 2-5 and Figure 2-6, refer
to three separate axis of measurement that correspond
to the orientation of the module (drawn in the center of
each plot).
The horizontal and vertical data, blue and red respec-
tively, in each plot correspond to the orientation (polar-
ization) of the measurement antenna rotated 360
degrees around the module.
The horizontal measurement was done with the receive
antenna parallel with the module PCB. The vertical
measurement was done perpendicular to the module
PCB.
These patterns allow the designer to understand the
performance of the module with respect to the position
of the receive/transmit antenna at the other end of the
link. Figure 2-4, Figure 2-5 and Figure 2-6 show the
simulated radiation patterns expected from the PCB
antenna.
DS70632A-page 16
Preliminary
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