LDLL16ENTR datasheet(40/102 Pages) STMICROELECTRONICS

40 / 102 page

Table 12. Unicast frame data - operating code and register address

Command byte (8-bit)

Operating code

Address

Bit

Name

OC1

OC0

The operation code is used to distinguish among different accesses modes to the registers of the responder

device.

Table 13. Unicast frame data - registers access mode

Bit 7 - OC1

Bit 6 - OC0

Meaning

A write operation leads to a modification of the addressed data by the payload if a write access is allowed (for

example control register, valid data).

A read operation instructs the responder to answer with a frame containing a global status byte and the data

present in the addressed register at communication start. Read operation instructions executed on specific

addresses initiate the responder to reply with a frame containing data present in the addressed register and the

three subsequent registers. This command is called burst read. In any case, the payload data of the commander

request will be ignored and internal data will not be modified.

A read and clear operation will instruct the responder to reply with a frame containing a global status byte and the

data present in the addressed register after the execution of the clear command. Furthermore, a read and clear

operation leads to a clearance of the addressed register status bits. The bits to be cleared are defined firstly by

address and secondly by the payload bits set to "1".

A read device information operation accesses the ROM device data (see ROM memory map).

Besides write, read, read and clear, there are two advanced operation codes. Both of them can be used to clear

all status registers, while one can be used to set all control registers to their default value.

A "set all control registers to default" and "clear all status registers" command is performed when an OpCode "11"

at address b’111111 is performed. A "clear all status registers" command is performed when an OpCode ‘10’ at

address b’111111 is performed.

The payload is the data transferred to the responder device with every unicast communication. The payload

always follows the OpCode and the address bits.

For write access the payload represents the new data written to the address registers.

For read operation the payload is not used. For functional safety reasons it is recommended to set the unused

payload to "0".

For read and clear operation, the payload indicates the clearance of specific bits in the status register. The bits to

be cleared are defined firstly by address and secondly by the payload bits set to "1".

Figure 29. Unicast diagnosis request frame

OP Code, Address

Data Byte 1

Data Byte 2

...

CTRL

CRC

ACK/EOF

,,00",Responder ID[8:0]

As shown in the Figure 29, the commander addresses a responder by its "Responder ID" in CAN FD ID.

LDLL16EN

Communication interface

DS14111 - Rev 5

page 40/102

LDLL16ENTR Datasheet(PDF) 40 Page - STMicroelectronics

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