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AS3935

Datasheet - Detailed Descri p ti on

8.4.4 Send Direct Command Byte

It is possible to send direct commands by writing 0x96 in the registers REG0x3C and REG0x3D, as shown in the table below:

8.5 I²C

An I²C slave interface is implemented for read/write access to the internal registers and to send direct commands. To enable the I²C as interface,

the Select Interface pin has to be set to the positive voltage supply (SI=VDD). The I2CL is the clock bus, while the I2CD is the data bus. An

external pull-up resistor on the I2CL pin is needed.

The device addresses for the AS3935 in read or write mode are defined by:

0-0-0-0-0-a1-a0-0: write mode device address (DW)

0-0-0-0-0-a1-a0-1: read mode device address (DR)

Where a0 and a1 are defined by the pins 5 (ADD0) and 6 (ADD1).

Figure 16. I²C Timing Diagram

Table 13. Registers 0x3C, 0x3D

Direct Command

Register

Description

PRESET_DEFAULT

0x3C

Sets all registers in default mode

CALIB_RCO

0x3D

Calibrates automatically the internal RC Oscillators

Table 14. I²C Parameters

Symbol

Parameter

Conditions

Min

Typ

Max

Units

Spike intensity

50

100

ns

High Clock Time

400 kHz Clock speed

330

ns

Low Clock Time

660

ns

I2CD has to change Tsetup before rising

edge I2CL

30

ns

No hold time needed for I2CD relative to

rising edge of I2CL

-40

ns

Within start condition, after low going I2CD, I2CL has to stay constant for

specified hold time

300

ns

After high going edge of I2CL, I2CD has to stay constant for the specified setup

time before STOP or repeated start condition is applied

100

ns

100

ns

I2CD

I2CL

start

T

LO

T

SU;DAT

sr

stop