Fema B Series, Руководство пользователя, Страница: 18 / 36

FEMA ELECTRÓNICA . SERIES B . Models Bxx-RTU
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As a standard, Modbus RTU protocol is designed to work with
registers of 16 bits. This allows to work with numerical values
between 32767 and -32767. In order to work with numerical
values up to 999999 and -199999, larger register of 32 bits
are needed
(see section 1.21.5)
. A 32 bits register is read and
written as if it was composed of 2 registers of 16 bits.
To write on 32 bits registers use function 16 ‘Write multiple
registers’ and to read on 32 bits registers use function 3
‘Read registers’. Working with 32 bits registers has the fol -
lowing limitations:
• registers of 32 bits (2 registers of 16 bits) must be writ -
ten or read using the same single function. It is not al -
lowed to write 16 bits with a function and then write the
following 16 bits in the next function.
• in case of writing (or reading) only a part of a 32 bits
register (only first 16 bits or last 16 bits) the instrument
will discard the write (or read) function. Instrument will
not transmit error code.
Available ‘functions’, ‘registers’ and ‘coils’ for each mode are
explained at sections
1.17, 1.18, 1.19 and 1.20.
In ‘Full slave’ mode, the ‘master’ controls the activation and
deactivation of each individual alarm in the ‘slave’ instru -
ment, by sending write functions to the appropriate regis -
ters or coils. By default, alarm control is performed by writ -
ing to coils. To switch to alarm control by writing to registers,
configure the menu ‘Alarm control’ (‘ AL.ct ’).
Alarm control by coil or register is selectable but only one
type of control can be active.
Available ‘functions’, ‘registers’ and ‘coils’ for each mode are
explained at sections
1.17, 1.18, 1.19
and
1.20.
The ‘watchdog’ function activates an error state in case of
loss of communication with the ‘master’. To configure the
‘watchdog’ indicate the maximum time accepted to wait be -
tween two frames received. If the configured time is exceed -
ed, the instrument activated the ‘watchdog error’. When a
correct frame is received, the ‘watchdog’ timer is reset.
Frames that can reset the ‘watchdog’ timer are those ad
-
dressed to the ‘slave’ instrument. These frames must con -
form to the Modbus RTU protocol and have a correct CRC.
If the function or register or coil indicated in the frame is not
correct, the ‘slave’ instrument will still reset the ‘watchdog’
timer. It will also reply with the corresponding error mes -
sage.
The internal alarms of the instrument can be associated to
the ‘watchdog’. In case of ‘watchdog’ activation, the associ -
ated alarm will also activate (see section 1.21.8) .
Display can also be configured to show an error message in
case of ‘watchdog’ error. It can be configured for flashing,
dash (‘------’) or to show message ‘Err.W’.
The instrument can be assigned any address between 1 and
247.
1.21.3 Addresses
1.21.4 ‘Watchdog’ function
1.21.5 16 bits or 32 bits registers
1.21.6 Alarm control : registers and ‘coils’