Rockwell Automation 842SPA User Manual

Installation Instructions

p

Bit Distribution

Bulletin 842-SPA Serial to Parallel Adaptor

IMPORTANT: SAVE THESE INSTRUCTIONS FOR FUTURE USE.

Specifications

Size 103 x 165mm (4 x 6.5in)

Voltage Supply 11-32V DC

Supply Current 250mA (without load)

Operating Temperature

Output Driver (parallel) PushĆpull, 10-32V, 35mA (max)

Input (SSI) RS422

Maximum SSI Cable Length 350m @ 125kHz; 25m @ 500kHz

0_C to 50_C (32_F to 122_F)

Mounting Instructions

1. Locate and mount the 842–CH cardholder (purchased
separately) close to the controller. See the Dimensions
section to determine the 842–CH card holder hole
locations.

2. Wire the connections according to the a) Electrical
Connections b) Jumpers Needed and c) Direction Control
sections using wire size 26–16 AWG.

IMPORTANT: Wiring must be in accordance with the

National Electric Code and applicable local
codes and ordinances.

3. Insert the 842–SPA into the cardholder. Set the Hex
Function switch on the 842–SPA to the appropriate setting
as shown in Table 1 below:

Switch
Setting

4 500kHz Binary Binary

4 500kHz Gray Gray

5 125kHz Binary Binary

5 125kHz Gray Gray

6 500kHz Gray Binary

7 125kHz Gray Binary

4. Apply power supply of 11–32V DC to the 842–SPA.

5. The 842–SPA begins sending clock pulses and receives
data pulses in the synchronous serial interface (SSI)
format. An example timing diagram is in the Timing
Diagrams section.

6. The parallel output data can be found on the following bits
according to Table 2 below:

842A Encoder

Type

A 8192 1-13 2048 14-24

B 4096 1-12 4096 13-24

C 2048 1-11 8192 12-24

D 4096 1-12 512 13-21

E 4096 1-12 256 13-20

Clock

Frequency

Pulses

Per Rev.

Bits Used
LSB-MSB

SSI

Input

No. of

Revs.

Parallel

Output

Bits Used

LSB-MSB

Electrical Connections

Type Function 842-CH Terminal

842-SPA and Output Driver

Ground

842-SPA Power

Power & Ground

SSI

Parallel Output
See Table 2 for
Bit Distribution

Ê Terminals are connected internally on the 842-SPA.

Ë The Error Bit is normally logic 0. If there is a power interruption (i. e. - low voltage)

during data transmission, the Error Bit is set to logic 1.

Parallel Output Driver

Power

Encoder Power 32A

Encoder Ground

Data + 26C

Data - 26A

Clock + 27C

Clock - 27A

Error Bit

Bit 1 3C

Bit 2 3A

Bit 3 4C

Bit 4 4A

Bit 5 5C

Bit 6 5A

Bit 7 6C

Bit 8 6A

Bit 9 7C

Bit 10 7A

Bit 11 8C

Bit 12 8A

Bit 13 9C

Bit 14 9A

Bit 15 14C

Bit 16 14A

Bit 17 15C

Bit 18 15A

Bit 19 16C

Bit 20 16A

Bit 21 17C

Bit 22 17A

Bit 23 18C

Bit 24 18A

1A, 2C, 25AÊ

32C,13CÊ

31A

1C,25CÊ

2AË

Jumpers Needed

Connect the following three jumpers:

1. 842–SPA Ground (Terminal 1A) to Encoder Ground
(Terminal 1C)

2. 842–SPA Power (32C) to Encoder Power (32A)

3. 842–SPA Power (13C) to Parallel Output Driver Power
(31A)

Direction Control

When pin 12 of the encoder is connected to DC + (or left
floating), the 842A will count UP when the shaft is turned CW
when looking at the shaft. When pin 12 is connected to DC
return, the 842A will count UP when the shaft is turned in the
CCW direction when looking at the shaft.

11

BITS

842–SPA

CLOCK +

842A

SSI
DATA +
VALUE

423 6579 1819202122

1

0

1

0

1

0000000001 1 11 11100 00000

8

TURNS

10

1314151617

12

1

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.

23

25

SHAFT POSITION

24

ERROR BIT

1

...

...

Dimensions

Use the figure below to locate the mounting holes of the 842–CH.

131

(5.16)

121

(4.76)

"A" Terminals

45

(1.77)

76

(2.99)

24

(0.95)

"C" Terminals

...9 7 5 3 131

...8 6 4 232

5.5

(0.22) Dia.

15 (0.59)

30

(1.18)

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Publication 75008–134–01(E)

Document 910 990 103 490

August 2001

Printed in Germany