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4. Software Implementation of the Gateway
4.2.8. Description of Services Assigned to Gateway Inputs/Outputs
Managing the downstream Modbus network: Please see chapter 5.2 Diagnostic only, page 37, for a detailed
description of this service. The example described in chapter 9.1 Main Program: “LAD 2 - MAIN_LUFP9”,
page 86, only automatically acknowledges gateway diagnostics, that is to say it does not exploit the data from
these diagnostics. In the case of the gateway’s default configuration, under AbcConf, the “Control/Status Byte”
field of the “ABC” element is equal to “Enabled but no startup lock.”
Periodic communications (inputs): The value of each of the 8 words for this service corresponds to the value
of the status register of a TeSys U motor starter (register located at address 455).
Periodic communications (outputs): The value of each of the 8 words for this service corresponds to the value
to be sent to the command register for a TeSys U motor starter (register located at address 704).
Please see chapter 9.2 Controlling/Monitoring Sub-Program for a TeSys U Motor Starter: “LAD 3 - CMD_MON”,
page 87, for an example of the simplified use of these “periodic communications” services.
Aperiodic communications: Please see chapter 9.3 Sub-Program for Reading a Parameter in all TeSys U
Motor Starters: “LAD 4 - RD_PAR”, page 89, and chapter 9.4 Sub-Program for Writing a Parameter on a Single
TeSys U Motor Starter: “LAD 5 - WR_PAR”, page 91, for an example of how to use the “aperiodic
communications” services.
These aperiodic communications services offer functions similar to those of “parameter area PKW”, which can
be found on certain Schneider Electric products, such as some ATV drives.
The 16-bit inputs and outputs for which the MSB and LSB order is specified must be
used by the DeviceNet master inverting the LSB / MSB order so as to restore the value
of the corresponding item of Modbus data.
• Sample reading of a motor starter parameter:
Reading of the 1st fault register (address = 452 = 16#01C4) on “TeSys U n°5” motor starter. The initial
values of O:1.16 and I:1.16 are equal to 16#1306. The result of the reading is 16#0002 (magnetic fault).
Output Value Meaning (MSB + LSB) Input Value Meaning (MSB + LSB)
O:1.10 16#0305 Function no. + Slave no. I:1.10 16#0500 Slave no. + (not used)
O:1.11 16#C401 Parameter address (MSB↔LSB)I:1.11 16#0203 Number of bytes + Function no.
O:1.12 16#0100 Number of parameters (MSB↔LSB)I:1.12 16#0200 Value read (MSB↔LSB)
O:1.16 16#1307 “Trigger byte” for the query (Pf) I:1.16 16#1307 “Trigger byte” for the response (Pf)
• Sample writing of a motor starter parameter:
Writing of the 2nd command register (address = 705 = 16#02C1) on “TeSys U n°7” motor starter at the value
16#0006 (clear statistics + reset thermal memory). The initial values of O:1.16 and I:1.16 are equal to
16#1307. The result of the writing is a command echo, that is to say that the values of the “address
parameter” and “value to be written” fields are identical in both the query and the response.
Output Value Meaning (MSB + LSB) Input Value Meaning (MSB + LSB)
O:1.13 16#0607 Function no. + Slave no. I:1.13 16#0607 Function no. + Slave no.
O:1.14 16#C102 Parameter address (MSB↔LSB)I:1.14 16#C102 Parameter address (MSB↔LSB)
O:1.15 16#0600 Value to be written (MSB↔LSB)I:1.15 16#0600 Value to be written (MSB↔LSB)
O:1.16 16#1407 “Trigger byte” for the query (PF) I:1.16 16#1407 “Trigger byte” for the response (PF)
Avoid writing incorrect values in outputs which correspond to the aperiodic communication
services described above, as they would lead to the transmission of an incoherent Modbus
frame. In fact there is no check on the data used by these services and so it is up to the
DeviceNet master PLC application to manage them.
In addition, do not ever use these services in “Broadcast” mode (Modbus address = 0).