BusWorks® Model 989EN U
ser’s Manual Modbus TCP/IP Digital I/O & Counters
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Description
Data Type/Format
Holding Registers (4x References, Read/Write)
40006
05
(0005)
Output Open-
Load Current
Enable for
DO0-15
Enables ~50uA
pull-down
currents at the
outputs for
open-load
detection with
inputs tri-
stated.
Def=0000H
(Open-Load
Disabled)
Data Format:
16-bit Unsigned Integer
For open-load detection with inputs tri-
stated, this register allows you to
enable/disable a 50uA open-load
detection pull-down current at the port
outputs. This only works if inputs are
tri-stated (wetting current pull-ups are
disabled).
0000H= Disable open-load pull-down
currents for the port (default).
FFFFH= Enable open-load pull-down
currents for open-load detection.
Note that open-load detection pulls
unused inputs to the ON state. Do
not enable if driving loads that may be
sensitive to ~50uA in OFF state.
40007
06
(0006)
Short Fault
Protection
Control (SFPC)
Output DO 0-15
Enables a fast
output shut-
down without
using an over-
temperature
trigger.
This allows the
protection to be
tailored for
inductive
versus
incandescent
lamp loads.
This is also
useful in
helping prevent
a shorted load
from blowing an
external series
fuse.
Fast fault
protection is not
reflected in the
I/O Error Status
bits.
Def=FFFFH
(Enable Fast)
Data Format:
16-bit Unsigned Integer
Outputs already have built-in current-
limiting and thermal shutdown
protection with programmable retry.
This is not the same thermal limiting
that applies to inputs. This register is
used to optionally select a fast
shutdown of the outputs when over-
current conditions are detected, but
thermal limits have not been reached,
such as with a shorted load. Thus, it
would be useful for tailoring outputs to
inductive loads or incandescent lamp
loads.
0000H = Thermal Only (Slower)
–
Output will rely on over-temperature
shutdown only (this is slower than Vds
based trigger). Outputs that
shutdown thermally are reported in
the port I/O status registers and can
optionally be automatically retried via
the GSRC register controls.
FFFFH = Drain-to-Source Voltage
(Faster)
– Output will shut down after
100-450us during turn-on into a short
circuit. The decision for shutdown is
based on an output drain-to-source
voltage > 2.7V. This provides
protection for loads that experience
higher than expected current and
require a fast shutdown. It is also
useful to prevent a shorted load from
blowing a series fuse.
Register Map
Model 989EN-4x16
IMPORTANT: Outputs that
utilize fast shutdown are not
subject to the automatic retry
mechanism of the GSRC
register. That is, faulted
outputs that are shutdown fast
do not retry their control until
reset, or optionally via the
output refresh cycle (when
enabled).
Outputs that were shutdown
fast in response to a fault are
also not reported in the Port
I/O Error Status registers.
