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5.19. Master Modbus Communication
5.19.1. Master communication blocks
With option "G = Master Modbus RTU Communication",
the device offers the Master Modbus RTU communication
mode.
The Master Modbus RTU mode provides the user with up to
20 Modbus objects from devices connected to the controller
as slave nodes or formits writing of the value of an internal
controller value onto remote devices.
The features of these objects are defined in the Master com-
munication blocks and can be intuitively set in the dedicated
set-up page, "Master Communication" on GF_eXpress.
ACCESS=READ ONLY or AC-CESS=READ/WRITE objects
may be used as:
• references for alarms (REFE)
• references for digital outputs (F.out) if the data is bit type
• references for analogue outputs (F.ou.C, Func) if the data is
word type
• input for Math Functions if the data is of word type
• input for Logic Functions if the data is bit type
and may be:
• displayed in Home.x as numerical data (dS.SP, dS.F) or as
a bar graph form (bAr.1, bAr.2, bAr.3)
• displayed and/or set in the "MASTE" submenu or the User
Menu
80209C_MHW_850-1650-1850_01-2020_ENG_pag. 240
ACCESS=WRITE ONLY objects may be used to write the
value of a controller value on a remote device (e.g. power
calculated by PID).
Objects may be grouped into two types of task
(SPEED=LOW or SPEED=HIGH) on the basis of the reading
and/or writing speed forformance desired.
Tasks are forformed alternately, and scanning times depend
on the number of objects with the same value for the SPEED
parameter.
Attention! Modbus data exchange may be
managed to slave devices guaranteeing response
times below the MASTER_TIM parameter (range
60...1000ms, default = 60ms). If no response is
received, scanning of the master will continue,
but the error will be recorded in the parameter
ERR.x= tim.O with x from 1 to 20 in the MASTE
submenu.
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