L6364 datasheet(16/60 Pages) STMICROELECTRONICS

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IO-Link UART peripheral

The L6364 contains an IO-Link UART peripheral for bidirectional communication according to the IO-Link

Standard.

The peripheral is controlled, and data is exchanged, via SPI register accesses. In an application where pins CQ

and DIO are coupled together i.e. JOIN mode, then a reference to CQ in the following refers to the shorted pair.

8.1

Multi-octet UART mode

8.1.1

SIO Mode

Figure 7 shows the IO-Link UART peripheral state machine. When the CCTL:SIO bit is set, the L6364 is set to

Single Input Output mode. In this mode the L6364 has the following states:

•

SIOActive: The CQ line is driven according to the setting of the HS and LS bits of CCTL register.

The internal UART does not run in this state and so master messages are only detected if a wake-up

request from the master is received, which switches the L6364 to the SIOListen state. If the output is set to

high impedance (CCTL:HS=LS='0'), then the L6364 can not receive a wake-up request from the master. It is

therefore necessary to switch to IO-Link mode (CCTL:SIO='0') if communication detection is required with a

high impedance output.

•

SIOListen: The L6364 has experienced a short-circuit via a wake-up request from the master.

Both high-side and low-side switches are off, and the restart timer is running. Transitions on the CQ line are

read as data, and stored in the data buffer (FR0 to FR14 registers). If a complete, valid, master message

is received, then the state changes to Transmit, an interrupt is generated and the restart timer is reset. If

the timer expires, then the L6364 returns to the SIOActive state and the CQ line is driven again after the

transmission.

8.1.2

IO-Link mode

At startup, and if the SIO bit is cleared, the L6364 enters IO-Link mode. In this mode the L6364 has the following

states:

•

IOListen: Transitions on the CQ line are read as data, and stored in the data buffers. Once a complete

master message has been read, or an error is experienced in reception (e.g. bad parity, checksum or

time-out), then the state changes to Transmit.

8.1.3

Transmit mode

Following reception of an IO-Link master message the L6364 enters the following state:

•

Transmit: The L6364 is waiting on data from the microcontroller, or is in the process of transmitting data on

the CQ channel. The L6364 reverts to IOListen or SIOActive on completion of the transmission, or if an abort

is generated by the microcontroller by setting END bit in the LINK register.

If the L6364 has entered Transmit from an SIO mode, the microcontroller would normally now set the L6364

to IO-Link mode, such that the L6364 continues to listen for further information from the master.

If the L6364 experiences a short-circuit during Transmit, then the STATUS:SSC bit is set, and the L6364

returns to either IOListen or SIOListen.

L6364

IO-Link UART peripheral

DS13363 - Rev 4

page 16/60

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