Installation and Set-up
1-3
SIMATIC TI505/TI500 MODNIM User Manual
Details
of the ASCII and RTU modes of transmission are listed in T
able 1-1.
T
able 1-1
T
ransmission Mode Characteristics
Characteristic ASCII RTU
Code used:
7 bits hexadecimal
(ASCII printable)
8 bits binary
Bits per character:
Start
1 1
Data 7 8
Stop 1 or 2 1 or 2
Parity Optional Optional
Checksum LRC CRC
NOTE:
On multidrop networks, the MODNIM requires a commercial modem
to connect to the Modbus network, as shown in Figure 1-1. The MODNIM
connected to a Series 505 PLC is equivalent to the use of the Modicon J475
modem interface with a Modicon PLC.
Programmable
Controllers
Modbus Network
Modem Modem
Multidrop
Configuration
Modem
MODNIM
Modbus
host
Modbus host
MODNIM
Point-to-point
Figure 1-1 Multidrop
and Point-to-point Configurations
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