JUMO mTRON T Manual page 68

6 User frames
NOTE!
When transmitting as a Modbus master, repetitive errors are entered in the event list. Corre-
sponding error codes can be found in chapter 3.9.3 "Error codes as integer return values".
Error monitoring
Each frame is monitored for data transmission. If an error occurs, the corresponding error flag
is set, an error code is also saved for each frame and an entry is written in the event list. This
entry is not cyclically generated and set; instead, it is generated and set once when the error
occurs and then again when the transmission functions again. The following applies to all
frames that are read:
if there is no valid response after 3 recurrences, all values of this frame are set to "no input val-
ue".
Block diagram of the inputs and outputs for the slave function
Ext. variables
Cyclical value check
and alarm generation
Frame processing
Write frames:
Data are collected.
Read frames:
Data are stored in
single variables.
Frame
config.
Reading/writing Modbus (slave)
(1) An external master makes a request (reading or writing).
(2) The interface receives the request.
(3) The corresponding Modbus table is used based on the device address.
(4) The Modbus table assigns the Modbus addresses to the device variables.
(5a) The variable value is accessed and the Modbus response is generated.
(5b) The frames configured for the Modbus master can also be accessed for checking or variable
scaling/type conversions.
68
(5a)
System I/O
With all
process values;
areas for 64
modules
Ext. variables;
limits checked
Ext. variables;
interface
cyclical
Additional
frames
(5b)
Modbus start adr.
+ frame length
(4)
Modbus
tables
for slave
With attributes
of every variable:
Type,
(5a)
address,
read only ...
(5b)
(3) (2)
Device Modbus
address slave
Serial and
Transfer TCP
in virtual
area
Modbus
master
Serial and
TCP
(1)
SCADA
system
PC
PLC
External
slave
devices