Manual epc10x

Figure 7: Message Structure

3.2 Bus Wire Considerations

The electromechanical design of a system using multiple epc10x devices on a twisted pair cable with an impedance of

typically 100 Ohms has an impact on the overall impedance of the system. Figure 8shows the change of the cable

impedance with smaller element pitch.

1.0 1.8 3.2 5.6 10.0 17.8 31.6 56.2 100.0

0

20

40

60

80

100

120

Pitch [cm]

Figure 8: Line impedance as a function of the element pitch

on a 100 Ohm twisted pair cable

terminate the bus line with an AC terminator network (shown in Figure 9) which matches the overall impedance of the

system according to Figure 8. In order to avoid high DC currents in the termination resistor, a capacitor of 100nF should be

connected in series to the termination resistor. The interface device has to be placed near the L/R circuit.

© 2013 ESPROS Photonics Corporation

Characteristics subject to change without notice

Page 9/29

Manual epc100 - V2.3-DRAFT 130812

www.espros.ch

Figure 9: Bus termination network

R

TE

C

TE

A

Device Address

Command

Parity Bits

A

A

C

P

D

P

Device Address

Command

Parity Bits

Parity Bits

Data

Register

P

P

Parity Bits

D

D

Data

A

A

Device Address

R

D

P

Parity Bits

Data

Register

Normal Command

Write Command

Results

Register Readout

C

A

A

Device Address

R

Register

P

P

Parity Bits

Command

Read Command