Siemens SINUMERIK 840C - Manual (Page 368)

07.97 6 NC Machine Data (NC MD), NC Setting Data (NC SD)
6.7.1 Axis-specific MD bits 2 (axial bits 2)
Description of function:
The absolute position is made up of
• 16 bits absolute revolution information (number of revolutions),
• 14 bits resolution within one revolution,
•
7 bits fine resolution,
i.e. that 2 16 = 65536 encoder resolutions can be displayed with a resolution of
max. 14+7 bits. The encoder has 2500 encoder lines, i.e. the 14 bit ”Resolution
within one revolution” is not exhausted (14 bits =16384 > 2500 · hardware
multiplication 4).
Information for the ”Position within one revolution” can therefore be derived with a
modulo (2500 · 4) calculation from the absolute value.
Because an overflow beyond the stated number of max. 65536 encoder
revolutions is expected when a absolute encoder for (endlessly turning) rotary axes
is used, an overflow compensation should be used here.
Here the function ”Single-turn absolute encoder available” provides the position
required in normal circumstances within one revolution from the absolute value
(run-up phase).
© Siemens AG 1992 All Rights Reserved 6FC5197- AA50 6–183
SINUMERIK 840C (IA)