AMIS-30621 datasheet(39/43 Pages) AMI

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9.2.4.6.1 Writing Frames

A writing frame is sent by the LIN Master to send

commands and/or information to the Slave nodes.

According to the LIN specification, identifiers are to be used

to determine a specific action. If a physical addressing is

needed, then some bits of the Data field can be dedicated

to this, as illustrated in the example below.

Another possibility is to determine the specific action within

the Data field in order to use less identifiers. One can for

example use the reserved identifier 0x3C and take

advantage of the 8-byte Data field to provide a physical

address, a command and the needed parameters for the

action, as illustrated in the example below.

Note

Bit 7 of byte Data1 must be at ‘1’ since the LIN specification

requires that contents from 0x00 to 0x7F must be reserved for

broadcast messages (0x00 being for the “Sleep” message).

The writing frames used with the AMIS-30621 are the

followings:

• Type #1: General purpose 2 or 4 Data bytes writing frame

with a dynamically assigned identifier

This type is dedicated to short writing actions when the bus

load can be an issue. They are used to provide direct

command to one (Broad = ‘1’) or all the slave nodes (Broad

= ‘0’). If Broad = ‘1’, the physical address of the slave node

is provided by the 7 remaining bits of DATA2. DATA1 will

contain the command code (see § 9.2.4.7), while, if

present, DATA3 to DATA4 will contain the command

parameters, as shown below.

• Type #2: 2, 4 or 8 Data bytes writing frame with an

identifier dynamically assigned to an application

command, regardless of the physical address of

the circuit.

• Type #3: 2 Data bytes writing frame with an identifier

dynamically assigned to a particular slave node

together with an application command. This

type of frame requires that there are as many

dynamically assigned identifiers as there are

AMIS-30621 circuits using this command

connected to the LIN bus.

• Type #4: 8 Data bytes writing frame with 0x3C identifier.

The structure is similar to Type #1 but uses the reserved ID

0x3C. Type #1 has the advantage to be shorter than Type #4.

AMIS-30621 LIN Microstepping Motordriver

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