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With Master operation, therefore other settings will result in generation of the next upper or
lower value according to above list. With all settings <250.0 kHz the error between set rate and
generated rate becomes negligible.
It is mandatory to set the Baud rate also with Slave operation. In this case, however, the
setting serves only to determine the pause time for correct synchronization (pause is detected
after 4 clock cycles). The unit automatically synchronizes with every remote clock signal within
the specified Baud rate range.
55.2. Evaluation of Encoder Bits
This chapter explains the correlation between the Basic Parameter „„BitS“ and the Operational
Parameters „„Hi bit“ and „„Lo bit“. The example below uses an encoder with 16 bits.
x
Unused Bits may be blanked out according to individual need
x
Whenever the number of bits (clock cycles) requested from the SSI Master is higher
than the real number of encoder bits, all excessive Bits must be blanked by
corresponding setting of parameters „Hi_bit“ and „Lo_bit“.
Basic Settings:
In general, parameter „BitS“ will always be set according to the real resolution of the encoder
(i.e. "BitS" = 16 with a 16 bit encoder). In this normal case the SSI telegram will not contain any
excessive bits.
With some applications (e.g. with Slave operation) it may however happen that the Master
transmits more clock cycles than the number of encoder bits (e.g. 21 clocks with a 16 bit
encoder). In such a case the master would always request 21 bits from the encoder, where the
encoder itself responds with 16 usable bits only, followed by 5 waste bits. These 5 excessive
bits must be blanked.
All standard SSI telegrams start with the most significant bit (MSB) and close with the least
significant bit (LSB). Unusable waste bits (X) will follow at the tail end. To blank these bits out,
in our example we would have to set „Hi bit“ to 21 and „Lo bit“ to 6 for proper evaluation of the
encoder information.
Hi
B
it
Î
Lo B
it
Î
Requested
Bits (Clocks)
21 20 19 18 17 16 15 14
13 12 11 10 9 8 7 6
5 4 3 2 1
Usable Bits
(encoder)
16 15 14
13 12 11 10 9 8 7 6 5 4 3 2 1
X X X X X
