Baumer G1-G2-GB-GXxxx - Manual (Page 27)

Manual_ProGeber_V1-40_EN.doc 27/40 Baumer IVO GmbH & Co. KG
10.05.11 Villingen-Schwenningen, Germany
4.4.2 Special bits SSI
In case of the „Special bits SSI“, the following special bits are added to the transmitted
data bits:
• DataValid
• Parity
The added special bit „DataValid“ serves as an additional error control in the encoder and
signalizes e.g. broken glass, LED failure, low supply voltage of electronically controlled gear
box.
The easiest procedure for the detection of errors is to add a parity bit during the transmission.
The parity of IVO encoders is even. In case of even parity, the added parity bit is set to zero
when the number of ones in the data word is even. It is set to one when the number is odd.
Thus, the total number of transmitted ones in one data word including the parity bit is always
even.
Note:
When a parity bit is set, it is always the even one
4.4.3 Number of data bits
If the „Output format SSI“ is set left-justified, it is possible to send zeros ("high-order zeros")
before the data bits. The number of data bits contains the data bits with the high-order zeros.
Example: In case of a 16-bit position value and a setting of 20 data bits, 4 high-order zeros
are sent in front of the position value before the left-justified telegram is sent.
4.4.4 Assigned outputs
Besides the SSI interface several special outputs are available. The number of outputs
depends on the encoder model, however it is limited to 4 maximum. The outputs may be
assigned in optional way to one of the following 6 functions, whilst the corresponding function
selected can be assigned exclusively to one output.
The outputs may be assigned to the following functions:
• Preset 1: Output triggers upon achieving the value entered.
• Preset 2: Output triggers upon achieving the value entered.
• RPM number control: Output triggers upon falling below the value entered.
Value input in turns/min.
• Battery control: Output triggers as soon as the voltage value for the lithium cell is falling
below the critical point. However, the encoder function still remains secure for another three
months.
• DataValid: Output triggers as soon as there is a code scanning failure.
• DataValid + battery control: Both functions are assigned to the same output as collective a
message.
4.4.5 Domain special outputs
The domain „special outputs“ is used to select the desired position or rpm at which the special
outputs are to switch.