Technology Option F01 08.2012
6SE7087-6QX70 (Version AN) Siemens AG
9-70 Compendium Motion Control SIMOVERT MASTERDRIVES
9.4.24 MDI mode [823]
Mode 3 "MDI" allows easy point-to-point positioning on the external
control system. The abbreviation "MDI" is derived from NC technology
and stands for "Manual Data Input".
A simple MDI positioning operation requires the following steps [823.5]:
♦
Step 1: Define an MDI block using 5 words (8 bytes) over the field
bus or select an MDI block, which is permanently stored in 3 indices
of a parameter. An MDI block comprises:
• G functions (1 word specifying whether positioning is absolute or
relative and − if desired − an acceleration factor)
• Position (1 double word, target position for absolute positioning
or distance to be crossed for relative positioning)
• Velocity (1 double word)
♦
Step 2: Define a start command [STA]
♦
Step 3: Wait until the "destination reached, axis stationary" status
bit [DRS] changes to "1"
→ the traversing operation is complete, the axis is in position.
These steps are described in detail below:
The first step is to define the desired MDI block. An MDI block
describes the reference data of a positioning operation and comprises 3
components:
♦ Two "G functions" (this expression is also derived from NC
technology):
The
first G function defines whether the traversing operation is to
be performed in absolute or incremental (relative) dimensions, i.e.
whether the specified target position refers to the home position or
the current position. On incremental measuring systems, the home
position is defined by the home position coordinate MD3 [823.4]; on
absolute encoder systems, it is defined by the zero point of the
position encoder. Only relative positioning is used on roll feeds.
The first G function can accept two values:
• 90 = Positioning in absolute dimensions
• 91 = Positioning in incremental dimensions
(relative positioning)
Point-to-point
positioning - it's
easy
Define the "MDI
block" [823.4...6]
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