Homepage
Modbus

contact:
mb_sfbe02

Modbus driver for PCD-xx7 / S7 Master / Slave

1. Overview:

Target: connection of Saia-Burgess PCD-xx7 or Siemens S7 to other PLC, PC, operator panels or other devices with MODBUS interface.

 

Supported functions:

- GOULD - MODBUS in RTU form

- PCD /S7 is slave or master

- interface RS485, RS422, RS232 according to installed interface module in     PCD / S7

- baudrate 300-38400 Baud (according to installed interface module)

- 7 / 8 data bits

- 1 / 2 stop bits

- Parity no / even / odd

 - slave address 1...255

- CRC (cyclical redundancy check) with cyclical block check table,

   check sum calculated with x16+x15+x2+1

- broadcast messages are only allowed for write functions 05, 06, 15, 16,      no answer

- end of telegram with time-out detection of 3,5 x character time

 

Used system functions:

- SFC 245: initialization of serial interface PCD-xx7

- SFB 12 BSEND Send PCD-xx7, CP441

- SFB 13 BRCV Receive PCD-xx7, CP441

- SFC64 TIME_TCK System time

 

MODBUS software

includes:

- function blocks for initialization of interface and data exchange with full 

  commentary, without knowhow protection for integration in your own         software

- data blocks for CRC and function blocks. User can rename blocks.

- manual

 

Master and Slave Modbus drivers are available.

Multi-Master, Multislave or Master and Slave are possible with different interfaces.

 

Master: Read or write of coil or input (only read) status or registers in one

           or more slaves. For example for reading or writing of datas from/to              external devices or PLC.

 

Slave: Write coil status or registers to a master or read coil status or                   registers from master with automatical translation into PCD                        memory.

            For example for reading or writing datas from/to a superior PLC,                 PC or an operator panel.

 

Ask for special versions, if required. Send your requiry to modbus@online.de.

 

Supported functions:

function code

1

2

3

4

5

6

7

8

11

12

15

16

function MODBUS

read coil status

read input status

read holding registers

read input registers

force single coil

preset single register

read exception status

loop back test

fetch communications event counter

fetch communications event log

force multiple coils

preset multiple registers

function for PCD

read bitwise

read bitwise

read words

read words

write 1 bit

write 1 word

read 8 exception bits (1 Byte)

---- (answer = request)

read status word and event counter

read status word, event counter, message counter and event bytes

write bitwise

write words

Address representation:

function code

1, 5, 15

2

4

3, 6, 16

data typ

output coil

input bit

input register

holding register

Modbus address

0xxxx

1xxxx

3xxxx

4xxxx

data typ

PCD is slave

M, O, T, C

M, I

DB

DB

M, O

DB

DI

DI

DI

DI

M, O

DB

Hardware requirements:

- enough free memory (up to 15 kByte)

- Modbus driver influences the cycle time according to the amount of

   exchanged datas

- communication module in PLC:

               PLC interface           communication module           PLC interface

 Saia-Burgess PCD-xx7:

               RS485/RS422          PCD7.F110                          interface 1

               RS232                      PCD7.F120                         interface 1

               20mA                       PCD7.F130                         interface 1

               RS485                      PCD7.F150                         interface 1

               RS232                      PCD2.F520/530                  interface 2

               RS485/RS422          PCD2.F5xx                          interface 3

 Siemens S7:

     RS232 or RS485/RS422    CP340 / CP341                   S7-300

     RS485/RS422                 S7 31x-C-PTP                 S7-31x-C

     RS232 or RS485/RS422    CP440 / CP441                   S7-400

 [Homepage] [Modbus]

Bild