Rockwell Automation 842A Absolute Encoder - Manual (Page 2)

Reset
To reset the output of the encoder to zero turns and zero shaft
position, remove the slotted cover from the back of the
encoder and press the button inside. This can also be done by
momentarily connecting pin 9 to DC+ Input.
ATTENTION: Pressing the reset button results in a
change of position reading. This can cause
unexpected motion which could result in damage to
the product, equipment, or personal injury.
Timing Diagrams
Below is an example of a timing diagram as viewed on an
oscilloscope. In this example, the 842A--31NB, a binary code
output with 4096 pulses per revolution and 4096 turns is
connected to an 842--SPA serial to parallel interface adaptor.
The 842--SPA generates an SSI clock burst of pulses. On the
positive slope of the start pulse, the 842A--31NB begins to
transmit its position data. In the example below, the
842A--31NB is returning 100000000011 (2051 Turns) and
001100000111 (775 position). After the data is sent, the output
remains in a low state for a short duration, then goes to a high
state in anticipation of the next SSI clock burst. The Error Bit
(bit 25) is normally zero. If there is a power interruption (e. g. --
low voltage) during data transmission, the Error Bit is set high.
0
0
1
1
TURNS SHAFT POSITION
0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 0 0 0 0 0 0 0
...
...
BITS
VALUE
842--SPA
CLOCK +
842A
DATA +
1
12
11
10 8
13
14
15
16
17
4 2 3 6 5 7 9 18
19
20
21
22
23
1 24 1
25
ERROR BIT
SSI
Dimensions—mm
M4
3 Plcs
7 (0.275) deep
9.0/11.0
(0.35/0.43)
5.98/5.99
(0.235/0.236)
13.5
(0.53)
13
(0.51)
4 (0.16)
3 (0.12)
3 (0.12)
24
(0.94)
22
(0.87)
27.8
(1.09)
59.5
(2.34)
34
(1.34)
49.94/49.98
(1.966/1.967)
25_
120_
Typ
42±0.1
(1.65)
60 (2.36)
66
(2.60)
Bulletin 842A--56**
58
(2.28)
51.5
(2.03)
8.8/9.2
(0.34/0.37)
9.98/9.99
(0.392/0.393)
18/20
(0.71/0.79)
18
(0.71)
10
(0.39)
13.5
(0.53)
13
(0.51)
4 (0.16)
3 (0.12)
M4
3 Plcs
7 (0.28) deep
24
(0.94)
22
(0.87)
27.8
(1.09)
120_
Typ
59.5
(2.34)
53.8
(2.12)
34
(1.34)
48±0.1
(1.89)
60 (2.36)
66
(2.60)
25_
35.94/35.98
(1.415/1.416)
Bulletin 842A--31**
Publication 75008--131 Ver 06
Document 910 990 103 488
February 2013
Printed in USA
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