TDC-GP21 datasheet(41/91 Pages) AMSCO

41 / 91 page

Ultrasonic-Flow-Converter

TDC-GP21

3-16

acam messelectronic gmbh - Friedrich-List-Str.4 - 76297 Stutensee - Germany - www.acam.de

3.4

SPI-interface

The serial interface is compatible with the 4-wire SPI standard. It needs the

SerialSelectNot (SSN) and can not operated as 3-wire interface.

SSN

- Slave Select

SCK

- SPI Clock

- SPI Data In

- SPI Data Out

The TDC-GP21 does only support the following SPI mode (Motorola specification)*:

Clock Phase Bit = 1

Clock Polarity Bit = 0

SCK starts with LOW, data take over is with the falling edge of SCK. The timings are

shown in section 2.3. The interrupt pin is set back to INTN = 1 if:



SSN goes LOW



or, in case SSN is already LOW, with the first rising edge of SCK.

SSN as Reset

The SerialSelectNot (SSN) line is the HIGH-active reset for the serial interface. After SSN

is set to LOW different operations can be addressed, not depending on the status of the

interface before the reset.

Note:

It is mandatory to set the SSN – line to High-state for at least 50 ns between each

Read-/Write sequence.

* There is no common SPI specification, especially for phase & polarity. Some microcontroller may

need a different setting, e.g. MSP430 run with Clock Phase = Clock Polarity = 0

Opcodes

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TDC-GP21 Datasheet(PDF) 41 Page - ams AG