PD6830X Explosion-Proof Modbus Scanners
Instruction Manual
23
Register Number (
ReG NUM
)
Enter the Modbus register number of the PV infor-
mation on the Modbus slave device defined in the
Slave ID
parameter.
Select 5-Digit or 6-Digit Register
Number
Data Type (
DATATYP
)
Enter the data type of the PV information in the Mod-
bus register. Selectable data types are float, short
integer, and long integer.
Use the
Up
and
Down
arrows to select the appropri-
ate data type and press
Enter
to accept.
For short and long integer types, select binary or bina-
ry coded decimal (BCD) formats as well as signed or
unsigned data format.
Byte Format (
BYTE
)
Select the PV data byte format as it is stored in the
Modbus slave device data register. Use the
Up
and
Down
arrows to select the appropriate data type re-
lated to endianness and byte order.
Byte Selection Byte Type
Description
1234
1234
Big endian
4321
4321
Little endian
2143
2143
Big endian with
byte swap
3412
3412
Little endian with
byte swap
Poll Time (
T POLL
)
Enter the time between read command sequences. In
other words, how often the display values are updated
in Master mode. The poll time defines how often the
device will begin scanning all enabled Modbus PVs.
For example, if the
Poll Time
is two seconds, the
scanner will begin polling all Modbus PVs every two
seconds.
This parameter defines the approximate time between
updates of a PV value. Communications errors may
make updating a PV take longer.
Note: Depending on the Response Timeout, and the
number of PV poll requests that time out, it may take
more than one poll time to poll all enabled Modbus
PVs. In this scenario, the scanner will begin another
round of polling at the next poll time interval.
For example: Due to transmission errors, the scanner
with a 2 second poll time requires 2.5 seconds to up-
date all the Modbus PVs. It will begin the second poll-
ing all the Modbus PVs at 4 seconds.
Note: The feet and inches display models enter this
value in the format XX.X seconds, but no decimal
point is present in the display. For example: enter 20
for a poll time of 2.0 seconds.
Response Timeout (
TIMEOUT
)
Enter the time the scanner will wait after a request for
information has been sent to a slave device before it
will assume an error on that request. Increasing the
timeout will help eliminate polling errors when polling
slow devices. Increasing the response timeout will
also slow the PV update rate in systems that are ex-
periencing communications failures.
Note: The feet and inches display models enter this
value in the format XX.X seconds, but no decimal
point is present in the display. For example: enter 20
for a poll time of 2.0 seconds.
Retries Before Error (
RETRIES
)
Enter the number of consecutive failures to poll a de-
vice that will result in a communications error mes-
sage on the display. This is the number of times a
specific PV must be polled before the display indi-
cates a communication failure rather than displaying
the available PV data. Increasing this number will
allow for more polling failures before a communication
error is detected, which may be required for some
unreliable networks. Increasing this number will also
increase how long old data is displayed before a
communication error is indicated.
