Siemens SIMATIC S7 System Manual page 10

Table of contents
8.5.1.8 Example of V memory and I/O address area ....................................................................... 433
8.5.1.9 User program considerations ............................................................................................... 435
8.5.1.10 LED status indicators for the EM DP01 PROFIBUS DP ...................................................... 437
8.5.1.11 Using HMIs and S7-CPUs with the EM DP01 ..................................................................... 439
8.5.1.12 Device database file: GSD ................................................................................................... 440
8.5.1.13 PROFIBUS DP communications to a CPU example program ............................................. 444
8.5.1.14 Reference to the EM DP01 PROFIBUS DP module technical specifications ..................... 446
8.6 RS485 .................................................................................................................................. 446
8.6.1 PPI protocol .......................................................................................................................... 447
8.6.2 Baud rate and network address ........................................................................................... 448
8.6.2.1 Definition of baud rate and network address ....................................................................... 448
8.6.2.2 Setting the baud rate and network address for the S7-200 SMART CPU ........................... 449
8.6.3 Sample RS485 network configurations ................................................................................ 451
8.6.3.1 Single-master PPI networks ................................................................................................. 451
8.6.3.2 Multi-master and multi-slave PPI networks .......................................................................... 451
8.6.4 Assigning RS485 addresses ................................................................................................ 452
8.6.4.1 Configuring or changing an RS485 address for a CPU or device in your project ............... 452
8.6.4.2 Searching for CPUs and devices on your RS485 network .................................................. 457
8.6.5 Building your network ........................................................................................................... 458
8.6.5.1 General guidelines ............................................................................................................... 458
8.6.5.2 Determining the distances, transmission rates, and cable lengths for your network ........... 459
8.6.5.3 Repeaters on the network .................................................................................................... 459
8.6.5.4 Specifications for RS485 cable ............................................................................................ 460
8.6.5.5 Connector pin assignments ................................................................................................. 460
8.6.5.6 Biasing and terminating the network cable .......................................................................... 462
8.6.5.7 Biasing and terminating the CM01 signal board .................................................................. 463
8.6.5.8 Using HMI devices on your RS485 network ........................................................................ 464
8.6.6 Freeport mode...................................................................................................................... 465
8.6.6.1 Creating user-defined protocols with Freeport mode........................................................... 465
8.6.6.2 Using the RS232/PPI Multi-Master cable and Freeport mode with RS232 devices ............ 468
8.7 RS232 .................................................................................................................................. 470
9 Libraries ............................................................................................................................................... 471
9.1 Library types (Siemens and user-defined) ........................................................................... 471
9.2 Overview of Modbus communication ................................................................................... 473
9.2.1 Modbus addressing .............................................................................................................. 473
9.2.2 Modbus read and write functions ......................................................................................... 475
9.3 Modbus RTU library ............................................................................................................. 476
9.3.1 Modbus communication overview ........................................................................................ 476
9.3.1.1 Modbus RTU library features ............................................................................................... 476
9.3.1.2 Requirements for using Modbus instructions ....................................................................... 477
9.3.1.3 Initialization and execution time for Modbus protocol .......................................................... 478
9.3.2 Modbus RTU master ............................................................................................................ 479
9.3.2.1 Using the Modbus RTU master instructions ........................................................................ 479
9.3.2.2 MBUS_CTRL / MB_CTRL2 instruction (initialize master) .................................................... 481
9.3.2.3 MBUS_MSG / MB_MSG2 instruction ................................................................................... 483
9.3.2.4 Modbus RTU master execution error codes ........................................................................ 487
9.3.3 Modbus RTU slave .............................................................................................................. 489
9.3.3.1 Using the Modbus RTU slave instructions ........................................................................... 489
9.3.3.2 MBUS_INIT instruction (initialize slave) ............................................................................... 491
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System Manual, V2.3, 07/2017, A5E03822230-AF
S7-200 SMART