Figure 1-1 Multidrop And Point-To-Point Configurations; Table 1-1 Transmission Mode Characteristics - Siemens SIMATIC TI505 User Manual

Modbus host
Modem
Modem
Multidrop Configuration
SIMATIC TI505/TI500 MODNIM User Manual
Details of the ASCII and RTU modes of transmission are listed in Table 1-1.

Table 1-1 Transmission Mode Characteristics

Characteristic
Code used:
Bits per character:
Start
Data
Stop
Parity
Checksum
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.
Modbus Network
Modem
Programmable Controllers

Figure 1-1 Multidrop and Point-to-point Configurations

ASCII
7 bits hexadecimal
(ASCII printable)
1
7
1 or 2
Optional
LRC
MODNIM
RTU
8 bits binary
1
8
1 or 2
Optional
CRC
Modbus host
MODNIM
Point-to-point
Installation and Set-up 1-3