gefran GPC, Configuration And Programming Manual, Page: 18 / 156

81901 “MSW_GPC-40/600A”_03-2021_ENG_page 16
To read these quantities in a single request, thereby reducing
the update times, simply do the following in GF_eXpress:
•
in the CustomVar1 object (address 200) enter the value
1026, i.e., the Modbus address of the first parameter to
be accessed;
• in the CustomVar2 object (address 201), the value
2050, i.e., the Modbus address of the second parame-
ter to be accessed;
• in the CustomVar3 object (address 202), the value
4098, i.e., the Modbus address of the third parameter
to be accessed.
At this point, through the Modbus read command of three
consecutive addresses starting from 0, the three powers
supplied can be accessed by means of a single operation.
3.4.3. Multi-node mode
This mode is activated by setting DIP switch 7 = ON.
The memory is organised in groups:
•
GPC-M for the controller’s M module variables.
• GPC-E1 for the controller’s E1 module variables.
• GPC-E2 for the controller’s E2 module variables.
The value set (Cod) on the rotary switches corresponds to
that of GPC-M; that of the other modules, if present, is in
sequence (Cod+1 for GPC-E1, Cod+2 for GPC-E2).
Examples
The rotary switches show the value 14. Therefore, node
(Cod) 14 addresses GPC-M, node 15 addresses GPC-E1
and node 16 addresses GPC-E2.
Using this setting, for example, the variable Ou.P in GPC-M
will have the address 14, 2 (=Cod, 2), the variable Ou.P in
GPC-E1 will have the address 15, 2 (=Cod+1, 2) and the
variable Ou.P in GPC-E2 will have the address 16, 2 (=
Cod+2, 2).
3.5. Time constraints of serial communication
In order to permit correct serial data exchange with the
device, the following time constraints must be respected:
• Reading register/word parameters
Reading n consecutive parameters, with n varying from
1 to 16, requires a time of:
– 40 ms with retentive memory enabled (default),
– 35 ms with retentive memory disabled.
The retentive memory setting is obtained through the
parameter EEP.E (see paragraph “3.26.2. Enabling
retentive memory storage”).
Thus, the next Modbus command to the same node,
whether read or write, must be sent after this delay
time has expired.
• Writing parameters to register/word
The writing of n consecutive parameters, with n varying
from 1 to 16 and a complete set of updated values (16
in total) with regard to those currently present on the
device, requires a time of:
– 40 ms + ( n x 10 ms *) with retentive memory ena-
bled (default),
– 35 ms with retentive memory disabled
The retentive memory setting is obtained through the
parameter EEP.E (see paragraph “3.26.2. Enabling
retentive memory storage”).
Thus, the next Modbus command to the same node,
whether read or write, must be sent after this delay
time has expired.
The times given refer to cases with a serial baudrate of
19200. Lower baudrates increase transmission times and
thus waiting times.
Notes
*) If the STATUS_W parameters (Modbus address 305) are
included in the write request, and their value is different
from the one currently present in the slave, the time
needed to write each one will be 30ms instead of 10ms
Note: The Custom map function is not available in Multi-node mode