AMIS-30621 Datasheet, PDF (37/59 Pages) AMI SEMICONDUCTOR – LIN Microstepping Motordriver

AMIS−30621
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−30621, are the
following:
Type #5: two, four or eight 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: eight 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. (Note:
because of the parity calculation done by the
master, the identifier becomes 0x7D as physical
data over the bus).
Preparing Frames
A preparing frame is a frame from the master that warns
a particular slave node that it will have to answer in the next
frame (being 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−30621 can be
of type #7 or type #8 described below.
Type #7: two data bytes writing frame with
dynamically assigned identifier. The identifier
of the preparing frame has to be assigned to
ROM pointer 1000, see Table 28.
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