MRF24WB0MASLASHRM datasheet(16/34 Pages) MICROCHIP

16 / 34 page

MRF24WB0MA/MRF24WB0MB

DS70632A-page 16

Preliminary

 2010 Microchip Technology Inc.

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

de-asserted

high

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.

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