User Manual
MODBUS Master Package for
W
INTERPRET
(T3837)
PD
-
6048 August, 96
(Issue 1)
4
Operation
The MODBUS function block uses control signals to report information and
accept runtime control
directives. The signals are user defined, and may be
used like normal Regent variables. Table 1 identifies these control signals.
Table
1
-
Control Signals
Name
Size
Type
Description
E
NABLE
Coil
Input
Enables execution of the function block. Energize to
execute the function block.
E
RROR
Coil
Output
Enunciates a MODBUS function block error.
Energized when an error occurs.
R
ESET
Coil
Input
Resets the error information. Energize to reset the
information. While energized, no errors w
ill be
reported.
N
ODE
Word
Output
The MODBUS node associated with the error. 0 when
there is no error.
C
ODE
Word
Output
The MODBUS function block error code. 0 when there
is no error.
T
IME
Float
Output
The time it took to complete the last MODBUS scan in
ms. 0 until a scan has been completed.
T
OGGLE
Coil
Output
This control signal changes state at the beginning of
each MODBUS scan. (Its period it typically
2
*
Time
)
E
NABLE
controls the execution of the function block at runtime. When
E
NABLE is de
-
ener
gized (OFF), the function block code is not executed
and all other signals are invalid (exception: the RESET
input signal will still be
honored).
E
RROR
enunciates any errors that the MODBUS function block code
encounters.
N
ODE
and
C
ODE
are used to further define an error. They are valid only
when
E
RROR is active.
N
ODE
contains the MODBUS node that is in error (
a zero [0] indicating the MODBUS master itself).
C
ODE contains the
specific MODBUS exception code.
The
T
OGGLE
state changes each time a MODBUS
scan is completed. After
the initial scan,
T
IME
contains the length (in ms) of the MODBUS scan.
T
OGGLE
is initialized to de
-
energized (OFF) for the initial scan. If a pulse is
desired instead of a toggle, external application code (in the same program)
may reset
T
OGGLE
to the de
-
energized state after a rising edge is detected.