Configuration of an absolute encoder
(Original Document)
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Role
Configuring an absolute encoder enables you to:
Procedure
The table below describes the procedure:
Step
Action
1
Select SSI absolute encoder or Parallel output absolute encoder in the input Interface field in the Acquisition configuration screen.
2
Click on Configuration... to display the following dialogue box:
3
Select the type of coding used by the encoder: Binary or Gray.
4
If necessary check the function Reading inversion.
This function modifies the value provided by the encoder in order to reverse the direction of the position.
5
Adjust the interrogation interval of the encoder according to the length of the frame and the length of the cable connecting the encoder. The module automatically determines the transmission frequency.
The diagram below can be used to select the optimum period, the value in brackets gives the transmission frequency determined by the module.
6
For an SSI absolute encoder:
Set the SSI frame characteristics used by the encoder:
  • number of bits on the frame heading are not significant N mini = 0, N maxi = 4 (0 is the default),
  • encoder data number of bits: N min. = 8, N max. = 25, (8 is the default),
  • number of bits of status N maxi = 3 (0 is the default),
  • number of bits sent after the last data bit excluding the parity bit,
  • presence or absence of the error bit (if the status field is not zero),
  • setting of the error bit (Number from 1 to 3) in the status bit zone,
  • logic level of the error bit (active at 0 or active at 1),
  • presence of parity bit (by default it is absent) and type of parity: Even or Odd (odd parity is not checked by the module).
Note: Number of header + data + status bits < or = 32
As the selections are made, the frame zone displays the elements of the frame.
Example: Frame: xxxx x8x xxE P.
xxxx = 4 header bits (one cross per header bit).
x8x = 8 data bits.
xxE = 3 status bits, one of which is an error bit positioned at number 1.
P = presence of parity bit, parity type: Even.
For a parallel output absolute encoder:
Set the characteristics of the SSI frame used by the encoder bearing in mind that the following values are set as standard:
  • number of frame header bits are not significant: 0
  • encoder data number of bits: 24
  • status number of bits: 3
  • number of error bit: 3 if error bit present
  • presence of parity bit and type of parity Even
7
Click on OK to confirm the choices made.