AMIS-30623 LIN Microstepping Motordriver
Data Sheet
16.6.2. Reading Frames
A reading frame uses an in-frame response mechanism. That is: the master initiates the frame (synchronization field + identifier field),
and one slave sends back the data field together with the check field. Hence, two types of identifiers can be used for a reading frame:
• Direct ID, which points at a particular slave node, indicating at the same time which kind of information is awaited from this slave
node, thus triggering a specific command. This ID provides the fastest access to a read command but is forbidden for any other
action.
• Indirect ID, which only specifies a reading command, the physical address of the slave node that must answer having been passed in
a previous writing frame, called a preparing frame. Indirect ID gives more flexibility than a direct one, but provides a slower access to
a read command.
Notes
(1) a reading frame with indirect ID must always be consecutive to a preparing frame. It will otherwise not be taken into account.
(2) a reading frame will always return the physical address of the answering slave node in order to ensure robustness in the communication.
The reading frames used with the AMIS-30623 are the following:
• Type #5: 2, 4 or 8 Data bytes reading frame with a direct identifier dynamically assigned to a particular slave node together
with an application command. A preparing frame is not needed.
• Type #6: 8 Data bytes reading frame with 0x3D identifier. This is intrinsically an indirect type, needing therefore a preparation
frame. It has the advantage to use a reserved identifier.
16.6.3. Preparing Frames
A preparing frame is a writing frame that warns a particular slave node that it will have to answer in the next frame (hence a reading
frame). A preparing frame is needed when a reading frame does not use a dynamically assigned direct ID. Preparing and reading
frames must be consecutive. A preparing frame will contain the physical address of the LIN slave node that must answer in the reading
frame, and will also contain a command indicating which kind of information is awaited from the slave.
The preparing frames used with the AMIS-30623 can be of type #7 or type #8 described below.
• Type #7: two data bytes writing frame with dynamically assigned identifier.
Preparing Frame
Byte
Content
Structure
Bit 7
Bit 6
*
Bit 5
0
Bit 4
ID4
Bit 3
ID3
CMD[6:0]
AD[6:0]
Bit 2
ID2
Bit 1
ID1
Bit 0
ID0
*
1
1
0
1
Identifier
Data 1
2
Data 2
Where:
(*)
According to parity computation
• Type #8: eight data bytes writing frame with 0x3C identifier.
SetDualPositioning Writing Frame
Structure
Byte
Content
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
0
0
1
1
1
1
0
0
0
1
2
3
4
5
6
7
8
Identifier
Data 1
Data 2
Data 3
Data 4
Data 5
Data 6
Data 7
Data 8
AppCMD = 0x80
CMD[6:0]
1
1
AD[6:0]
Data4[7:0]
Data5[7:0]
Data6[7:0]
Data7[7:0]
Data8[7:0]
Where:
AppCMD:
CMD[6:0]:
AD[6:0]:
If = ‘0x80’ this indicates that Data 2 contains an application command
Application Command “byte”
Slave node physical address
Datan[7:0]: Data transmitted
AMI Semiconductor – June 2006, Rev 3.0
www.amis.com
45
AMI [ AMI SEMICONDUCTOR ]
