Operating Instructions
Chapter
8
DME4000
8014584/ZN33/2017-07
© SICK AG • Germany • Subject to change without notice
105
Troubleshooting and
Explanation of Terms
The max. cable length is dependent on the transmission speed; see Table 2.
The entered cable lengths can be extended using repeaters. We recommend not connecting more than
3 repeaters in a series. The DME supports all transmission speeds cited in Table 2.
Baud rate (Bit/s)
9.6 K
19.2 K
45.45 K
93.75 K
187.5 K
Range/Segment (m)
1200
1200
1200
1200
600
Baud rate (Bit/s)
500 K
1.5 M
3 M
6 M
12 M
Range/Segment (m)
200
200
100
100
100
Table 2: Range Dependent on the Transmission Speed
8.2.2
RS 422
The RS 422 standard fulfills requirements for fast and reliable data transmission.
This interface has been designed for serial data transmission in a completely duplex method with a
transmission rate of up to 10 MBaud and 1000 m cable lengths (German Industrial Standard, Part 3).
The interface is operated with send one data channel (T) and one reception data channel (R). The high
degree of transmission reliability is achieved by the valuation of the differential voltage between pair
core wires each time.
8.2.3
SSI
Data transmission with “SSI” setting is carried out at request of the control unit, whereby cycle time and
transmission speed can be set in extensive limits.
A clock sequence is set at the input of the DME for this from the connected control unit. With each
positive edge of clock pulse, a data bit is pushed on the DME send line with the highest value bit. There
is a clock pulse space of at least 30
µ
s between two clock sequences. The bit clock is between 70 kHz
and 500 kHz and is dependent on the cable length.
Cable Lengths [m]
Transmission Rate [kBaud]
<
25
<
500
<
50
<
400
<
100
<
300
<
200
<
200
<
400
<
100
Impulse Diagram of Data Transmission
m = stored parallel information
tv = delay time for the 1
st
clock pulse, max. 540 ns, for all further ones, max. 360 ns
Gn = highest value bit in gray code
T = period duration of the clock pulse signal
GO = lowest value bit in gray code
tm = monoflop time 15
µ
s to 25
µ
s
Tp = clock pulse space
Clock pulse
Serial data
Parallel data
Monoflop P/S
