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AS3932

Datasheet - Detailed Descr i p ti on

8.2.3 Serial Data Interface (SDI)

This 4-wires interface is used by the Microcontroller (µC) to program the AS3932. The maximum clock frequency of the SDI is 2MHz.

Note:

SDO is set to tristate if CS is low. In this way more than one device can communicate on the same SDO bus.

the data is sampled on the falling edge of SCLK. The Table 9 shows how the command looks like, from the MSB (B15) to LSB (B0). The

command stream has to be sent to the SDI from the MSB (B15) to the LSB (B0).

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 Table 10.

In case a write or read command happens the next 6 bits (B13 to B8) define the register address which has to be written respectively read, as

shown in Table 11.

Table 8. Serial Data Interface (SDI) pins

Name

Signal

Signal Level

Description

CS

Digital Input with pull down

CMOS

Chip Select

SDI

Digital Input with pull down

CMOS

Serial Data input for writing registers, data to

transmit and/or writing addresses to select

readable register

SDO

Digital Output

CMOS

Serial Data output for received data or read

value of selected registers

SCLK

Digital Input with pull down

CMOS

Clock for serial data read and write

Table 9. SDI Command Structure

Mode

Register address / Direct Command

Register Data

B15

B14

B13

B12

B11

B10

B9

B8

B7

B6

B5

B4

B3

B2

B1

B0

Table 10. SDI Command Structure

B15

B14

Mode

00

WRITE

0

1

READ

10

NOT ALLOWED

1

1

DIRECT COMMAND

Table 11. SDI Command Structure

B13

B12

B11

B10

B9

B8

Read/Write register

00

000

0

R0

00

000

1

R1

00

001

0

R2

00

001

1

R3

00

010

0

R4

00

010

1

R5

00

011

0

R6

00

011

1

R7

00

100

0

R8

00

100

1

R9