DocID025240 Rev 2

3/25

AN4355

The L6480 and L6482 communication interface

25

1

The L6480 and L6482 communication interface

The device (always slave) can be driven by an MCU (always master) sending commands

through an 8-bit SPI interface. The 8-bit shift register of the device is kept enabled while the

CS input is forced low. During this time, at every raising edge of the serial clock (CK), the

SDI input is stored into the shift register. At CK falling edges the SDO output is updated

according to the last bit of the shift register.

When the CS input is raised, the device catches the shift register content and interprets its

value as a command or an argument of the previously received command.

All the bytes are sent through the SPI data lines starting from the most significant bit.

1.1

Communication protocol

The communication protocol is based on single byte commands that can be followed by

a command argument up to 3 byte long which must be transmitted starting from the most

significant byte.

Part of the information needed to execute the target operation could be embedded into the

command byte, for example the target register address in the GetParam and SetParam

commands, and the argument provides extra data as well as the target position of the GoTo

command.

By default the response byte of the device is h00 (hexadecimal format). Some commands,

for example those used to read the value of a register, generate a response from the device

up to 3 byte long which is transmitted during the following transmission cycles starting from

the most significant byte.

1.2

Daisy chain

The device is compatible with the daisy chain architecture allowing the MCU to drive

multiple devices with a single SPI interface.

The daisy chain architecture is obtained as follows:



Master serial clock line is connected to the CK input of each slave device.



Master slave select line is connected to the CS input of each slave device.



Master serial data output (MOSI) is connected to the SDI input of the first slave of the

chain.



The SDO output of each slave device is connected to the SDI input of the next one, last

slave excluded.



Master serial data input (MISO) is connected to the SDO output of the last slave of the

chain.