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5-4 Communication protocol for serial
output
The communication of the serial interface provides various possible operation modes
depending the dip-switch setting. All of them respect the following timeline:
Host sends interrogation code
F3EM2 reply with acquired data & cleans the data memory.
F3EM2 starts again with data acquisition & waits for next interrogation code
The interrogation codes can be set by dip switches 4+5 (see chapter 5-1 on page 5-2).
Note:After power-on F3EM2 starts automatically with data acquisition (without interrogation code).
The communication can also be forced by signal on the STROBE input (PNP logic); the light
curtain responds on the serial line with the desired data.
Note: This STROBE line can be used also as a check for the correctness of the serial wiring and/or
communication protocol.
The different operation modes are described below.
Bitmap of optics
Dip switch setting:
6
OFF
The light curtain responds with a serial of bytes. The quantity of bytes depends on the total
number of beams.
Each beam status is reflected by one bit. The beam index numbers are addressed to bits as
shown in the example below. Remaining unused bits in the last byte are set to zero.
E.g. the response of a light curtain with 20 beams is 3 bytes.
The numbers in the table reflect the beam index No:
st
1
byte
nd
2
byte
rd
3
byte
The beam with index 1 starts opposite from the connector.
As a result each response byte contains 8 beams. The following formula applies
for the calculation if the number of response bytes:
The maximum number of optical beams that can be managed by serial interface is 400.
F3EM2 MEASURING LIGHT CURTAINS OPERATION MANUAL
5-4 Communication protocol for serial output
7
8
OFF
OFF
Bitmap of optics (default)
1
2
3
4
9
10
11
12
17
18
19
20
Number of bytes
=
INT number of optical units
Type of function
5
6
7
8
13
14
15
16
0
0
0
0
8
+
7
5-5
5
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