MRF24WG0MA_12 Datasheet, PDF (15/38 Pages) Microchip Technology – MRF24WG0MA/MB Data Sheet 2.4 GHz IEEE 802.11b/g™

2.4 Serial Trace Port Interface
The MRF24WG0MA/MB incorporates a Transmit Data
pin (DEBUGTX) and a Receive Data pin (DEBUGRX) for
serial debugging purposes. These pins can be con-
nected to commercially available RS-232 line drivers/
receivers with appropriate external level shifters. The
serial interface operates at 19200 (baud rate), 8 (data), N
(parity), 1 (stop bit), N (flow control).
2.5 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 (logic low) by the
MRF24WG0MA/MB module. The INT line is de-
asserted (logic high) by the MRF24WG0MA/MB after
the data is transferred to the host PIC microcontroller.
The SPI SCK frequency can be up to 25 MHz.
The slave SPI interface implements the [CPOL = 0;
CPHA = 0] and [CPOL = 1; 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.
The CS pin must be toggled with transfer blocks and
cannot be held low permanently. The falling edge of CS
is used to indicate the start of a transfer. The rising
edge of CS is used to indicate the completion of a
transfer.
Figure 4-1 in Section 4.0 “Electrical Characteris-
tics” shows the SPI timing diagram. Table 4-7 details
the SPI timing AC characteristics.
MRF24WG0MA/MB
2.6 PCB Antenna
For the MRF24WG0MA, 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 in Section 1.0 “Device Overview”.
The antenna patterns shown in the following plots are
simulated results of the PCB antenna. Figure 2-4 illus-
trates the simulation drawing and Figure 2-5 and
Figure 2-6 illustrate the two-dimensional (2D) and
three-dimensional (3D) radiation patterns.
The calculated average of the radiated field is shown in
Figure 2-5, highlighted in yellow. The radiation pattern
for the XZ plane is shown in red, and the YZ plane is
shown in black. As shown, the most powerful radiation
occurs in the XY plane (the red pattern).
Figure 2-6 shows the relative position of the 3D radia-
tion “donut” with reference to the module orientation.
This is a very useful guide for placement of the module
to obtain the maximum range.
Figure 2-7 shows the 3D radiation pattern with the col-
ored distribution of the radiation magnitude. The values
range from -9 dB to +0.3 dB. This is very useful in
interpreting the 2D radiation pattern.
 2012 Microchip Technology Inc.
Preliminary Information
DS70686B-page 15