Data Sheet

iolinker Family Data Sheet

4 Protocol

4.1 General Message Format

Messages to the device are of the format

Slave address Command byte Argument bytes

Messages from the device are of the format

Reply argument bytes

Replies are only sent for read operations (W=1, compare table 2).

The MSB of the command byte is always 1, and the MSB of all other bytes is 0. This

makes it easy to recognize the start of a new message.

This general message format is slightly varied in SPI and in I2C mode, as described in the

following sections.

4.2 SPI Message Format

Messages

to the

device

Command byte Argument bytes 0x00 0x00 ... 0x00

Messages

from the

device

– – – Reply byte 1 ... Reply byte n

The slave address byte is left out, for slaves are selected via the Slave Select (SS) pin.

To read in the reply from the FPGA, the SPI master keeps sending out zero bytes n + 1

times after its command and command arguments. With one byte delay, the FPGA slave

will write back its reply argument bytes.

4.3 I2C Message Format

Messages to the device are of the format

Command byte Argument bytes

Messages from the device are of the format

Argument bytes

The slave address byte is left out, as it is encoded in the I2C protocol already.

 2017 jInvent. The speciﬁcations and information herein are subject to change without notice.