Network Communications; Modbus Data Mapping - Siemens 353 User Manual

UM353-1B

5.0 NETWORK COMMUNICATIONS

This section provides an overview of the data that can be obtained from the 353 using Modbus, or Modbus/TCP
Ethernet, which provides Modbus over Ethernet protocol. In the Modbus/TCP protocol all listed Modbus items are
available and are embedded in the Modbus/Ethernet protocol frame. Refer to Section 6 Data Mapping for detailed
list of the actual data. Go to the Modbus-IDA Website
and access to Modbus technical specifications.

5.1 MODBUS DATA MAPPING

Modbus is a master/slave protocol where a master device (e.g. PC-based operator workstation) sends commands to
one slave (i.e. Siemens 353 Process Automation Controller) and waits for a response. When using RS485 network
communication, each station has a unique network address (1-32), configured as part of the station parameters.
When using Modbus/TCP protocol each station has a unique IP address. Ethernet enables all 353 controllers on the
Ethernet network to be masters, thus providing peer-to-peer network relationships between controllers.
Data is assigned to either a register (16-bit word) or a coil (1-bit). An IEEE floating point number (Real) is
assigned to 2 consecutive registers with the first containing the most significant and the second the least significant
portion of the floating point number. The 353 uses an IEEE reverse format. See Table 3-4 in Section 3.2.7 AIE_-
Analog Input – Ethernet for more information on floating point formats.
The station supports Modbus function codes 01, 02, 03, 04, 05, 06, 08, and 16. Section 6 Data Mapping provides a
listing of available data and specific locations within the Modbus map. The following is the overview for the
complete 353 series controllers Modbus data mapping.
Station Coils......................................................................................x0001 - x0071
Loop Coils.........................................................................................x0296 - x1495
Extended Loop Coils (ODD Pushbuttons)........................................x8701 - x9100
Sequencer Loop I/O Coils (ref. MSLCP pointer) ............................x1496 - x2263
LonWorks Remote I/O Coils (352P, 353"A", & 354/354N) ............x2401 - x3976*
Ubus Discrete I/O States & Forcing (353R) .....................................x4001 - x5500
(spares)..............................................................................................x5501 - x9100
Loop PCOM Block Coils ..................................................................x9101 - x9999
Station Data (16-bit integer)..............................................................x0001 - x0100
Station String Data (ASCII) ..............................................................x0101 - x0200
Loop Dynamic Data (16-bit integer).................................................x0201 - x0450
Loop Variable Data (16-bit integer)..................................................x0451 - x1200
Loop Static Data (16-bit integer) ......................................................x1201 - x1950
Loop Dynamic Data (32-bit floating point) ......................................x1951 - x2450
Loop Variable Data (32-bit floating point) .......................................x2451 - x3950
Loop Static Data (32-bit floating point)............................................x3951 - x5450
Loop String Data (ASCII).................................................................x5451 - x7950
Ubus Module Types (353R)..............................................................x7951 - x8000*
Loop Trend Data (ref. MLTP pointer) ..............................................x8001 - x9000
(spares)..............................................................................................x9001 - x9999
* Areas of the map that apply to other 353 products and do not apply to the 353 Design Level B.
April 2012
http://www.modbus.org/ for more information on Modbus
Network Communications
5-1