AS3933 datasheet(27/64 Pages) AMSCO

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[v1-08] 2015-Sep-02

AS3933 − Detailed Description

Serial Peripheral Interface (SPI)

This 4-wire interface is used by the Microcontroller (

μC) to

program the AS3933. The maximum clock operation frequency

of the SPI is 6MHz.

Figure 25:

Serial Peripheral Interface (SPI) Pins

Note(s): SDO is set to tristate if CS is low. In this way more than

one device can communicate on the same SDO bus.

SDI Command Structure. To program the SPI the CS signal has

to go high. A SPI command is made up by a two bytes serial

command and the data is sampled on the falling edge of SCLK.

The Figure 26 shows how the command looks like, from the MSB

(B15) to LSB (B0). The command stream has to be sent to the SPI

from the MSB (B15) to the LSB (B0).

Figure 26:

SDI Command Structure

The first two bits (B15 and B14) define the operating mode.

There are three modes available (write, read, direct command)

plus one spare (not used), as shown in Figure 27.

Name

Signal

Signal Level

Description

Digital Input

CMOS

Chip Select

SIN

Digital Input

CMOS

Serial Data input for writing registers, data

to transmit and/or writing addresses to

select readable register

SOUT

Digital Output

CMOS

Serial Data output for received data or

read value of selected registers

SCLK

Digital Input

CMOS

Clock for serial data read and write

Mode

B15

B14

B13

B12

B11

B10

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