IF51
SSI High Bit
This register defines the highest bit (MSB) for evaluation, when the bit blanking
function is used. See “Hint for the use of the bit blanking function” below in this
page.
It must be set to the total number of encoder bits for evaluation of the full
encoder range.
EXAMPLE
In the following example a 13-bit encoder is shown with
set to 03, resulting in evaluation of bits 03 to 12 only and
blanking out positions 01, 02 and 13.
13 12 11 10 09 08 07 06 05 04 03 02 01
(Hi_bit = 12, Lo_bit = 03)
Evaluated encoder bits
(LSB)
(M SB)
High order bit
Low order bit
Hint for the use of the bit blanking function
Bit blanking results in a different evaluation of the encoder information, thus
you should be fully aware of what happens with the resolution and the number
of registered turns when you use this function.
EXAMPLE
In the following example two different results when blanking out one bit in a
13-bit single-turn encoder are explained.
•
Without blanking, a 13-bit encoder would provide 0 – 8191 information
at each 0 - 360º turn of the encoder shaft.
This would assume a setting of
01.
It is easy to understand that there are two different ways to use only 12 of the
13 bits available:
•
blanked the high order bit. The result corresponds to an encoder
providing 0 – 4095 information while we turn from 0 - 180º, and again
the same 0 – 4095 information while we continue from 180º to 360º.
The resolution remains unchanged as far as the number of steps per
revolution is concerned.
•
We can also keep the
to 02 instead. This means we blank the low order bit now. As a
result, within one turn of 0 - 360º, we receive the encoder information 0
– 4095 one time only, thus the total number of steps per revolution is
down by half.
MAN IF51 I_E 1.1.odt
10 - Parameter settings
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