ElmoMC CANopen DSP 402 Implementation Guide - Manual (Page 96)

CANopen DSP 402 Implementation Guide
MAN-CAN402IG (Ver. 1.2)
90
Sub-index 6
Description Buffer
clear
Entry category Mandatory
Access Write only
PDO mapping No
Value range UNSIGNED8 (described below)
Default value 0
Notes:
The maximum and actual buffer size are the number of interpolated data records
that may be sent to the drive to fill the input buffer. They are not the size in
bytes. The actual buffer size may be between max buffer size to.
The buffer position has an effect when the ring buffer is selected.
The buffer organization may change only when interpolated mode is not active.
Reorganization of the buffer clears the input buffer.
Buffer can be clear by sub-index 6 only if interpolation is not active.
Buffer strategies
The contents of the buffer items can only be accessed via the interpolation data record. The
maximum buffer size is given in object 0x60C4 is used by the host to determine the actual
buffer size.
Commonly, first-in-first-out (FIFO) structures or ring buffers are used as input buffers.
FIFO:
If the buffer is organized as FIFO, every new received interpolation data record is
placed at the end of the queue, and the drive takes the next data record from the top
of the queue. When the last item of a data record is stored, the buffer pointer is
incremented in order to point to the next buffer position. With this buffer principle,
the object buffer position has no affect. The FIFO buffer is organized as a cyclic buffer
so that after the last buffer entry is updated (entry of max buffer size), the first entry
may be available again depending on actual buffer size. When the buffer is full, an
emergency is transmitted and the last message is discarded.
If buffer is empty interpolation is disabled and emergency may be transmitted if
o CANopen Implementation Guide). defined so by object 0x2F21 (refer to the Elm
Ring buffer:
If the buffer is structured as a ring, the host can place an interpolation data record into
any valid position in the ring by changing the pointer defined in buffer position.
Without changing the buffer position, all data records are written at the same location.
The drive reads the next entry out of the buffer by an internal ring pointer. It is set to
the first data record with buffer clear, after the reorganization of the input buffer. The
user cannot exceed the max buffer