Jetter JetWeb JX2-CNT1, Руководство пользователя

Страница: 77 / 100

JX2-CNT1 11 SSI Absolute Encoder
Jetter AG 77
11.3 Reversal of Counting Direction
The counting direction for SSI position values can be reversed by means of bit 9 "SSI
- Reversal of counting direction" in register 3xx3 "Status / Controller". For more
information refer to chapter 8.1 "Status and Control Functions", page 55.
11.4 Parity Check
The JX2-CNT1 is able to perform automatic parity checks. For correct parity checks
the following requirements have to be fulfilled:
• Parity check must be set correctly (even or odd parity)
• Parity check must be enabled
• The number of clocks must be set correctly
• The connected SSI encoder must include
one parity bit at the end of the data
stream .
For more information on setting and enabling parity check please refer to
“Configuration" on page 75. For information on how to set the correct number of
clocks refer to “Reading in SSI data" on page 69. If the SSI encoder provides a parity
bit in the data stream, this bit must be taken into account when specifying the number
of clocks in register 3xx6 "SSI configuration". That is, if, for example, the encoder
provides 24 position bits and one parity bit, the number of clocks must be set to 25
bits.
If the SSI encoder performs parity evaluation can be seen from the manual that
comes with the encoder.
If the JX2-CNT 1 module detects a parity error, the position value received is ignored
(
register 3xx0 "Count value" is not updated ) and register 3xx7 "Counter of SSI
parity errors" is incremented.
Important!
Binary Coding : If DATA + and DATA - are correctly connected to the encoder,
the JX2-CNT1 indicates that the counting direction is reversed compared to the
counting direction of the encoder. In order to maintain the original counting
direction in JX2-CNT1, the counting direction must be reversed.