Data Formats; Faulty Ssi Query - Balluff BTL7-S5 M J-DEXC-TA12 Serie Manual De Instrucciones

BTL7-S5_ _ (_)-M_ _ _ _-J-DEXC-TA12
Magnetostrictive Linear Position Sensor – Rod Style
6
SSI interface (continued)
6.2

Data formats

The BTL7 Standard transducer has the following factory
settings for position output, which can no longer be
changed retroactively:
– SSI24, SSI25 or SSI26
– Binary or Gray coded
– Rising or falling
The contents of the information to be transferred and the
error value can be configured with the BTL7-S510....
Position, velocity, or differential position/velocity can be
sent via Data. The MSB is always transmitted first.
SSI16
Clk
1 2 3
Data
15 14 13
MSB
Fig. 6-1: Example of a complete SSI16 data transmission
Depending on the configuration, position or speed data
may have a leading sign with the BTL7-S510.... Negative
values are output as a two's complement. With positive
speeds, the magnet moves away from the electronics
head; with negative speeds it moves towards the
electronics head. The controller must be set to process
signed data then.
6.3

Faulty SSI query

Underclocking
If there are too few clock edges, the current data level will
be maintained for the time t
after the last negative edge from Clk. If, however, another
positive edge occurs, the next bit will then be output.
Afterwards, a T event will occur internally, the data output
o
switches to low and then back to high after the time t
elapsed. The high level is maintained until the next clock
burst. Time t starts after the end of time t
m
Overclocking
If there are too many clock edges, the data output will
switch to low after the correct number of cycles has been
completed. The t timer is started again for every
m
additional negative edge from Clk and the T
internally. DATA switches back to high after the time t
elapsed.
18 english
4 5 6 7 8 9
12 11 10 9 8
(t = 2 · T timeout times)
o o Clk
has
m
.
o
event is set
m
has
m
23
m
Output of a position via SSI24
m = MSB (Most Significant Bit)
L = LSB (Least Significant Bit)
25 24 23 22 21 20
0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Example of an SSI26 with an error bit in bit location 21 and
error value 0. The data length is 21 bits, the total bit
number is 26. Four zeros are transmitted before the error
bit.
10 11 12 13 14 15
7 6 5 4 3 2
A T or T event is displayed in the status field as a
o m
communication error in the Micropulse Configuration Tool.
In short, a communication error is caused by the following:
– The bit number set in the transducer does not
correspond to the bit number in the controller.
n > n  T
BTL PLC o
n < n  T
BTL PLC m
– The SSI clock frequency is too low
f < 9.771 kHz  T
Clk
– The pause between two clock packages is too short
event
 T
m
Ignition protection "d"
Flameproof enclosure
Position
Error value or position value
16 17
1 0
LSB
event
event
event
o
0
L
0