GE 8122-DI-DC 16-channel DI, 24Vdc isolated, sinking
GENERALDO modules can provide up to 4 or 8 discrete
outputs, depending upon module type. Line
fault detection is also provided on the 2/1
modules for both open- and short-circuit
conditions.
Output Mode
The DO module outputs may be configured
for one of three different types of output:
• Discrete
• Single pulse
• Continuous pulse
Discrete
The Bus Interface Module (BIM) or Controller
signals an ON or OFF condition on demand.
Singe Pulse (See Notes 1 & 2)
This is an individual “single-shot” action,
creating a single ON pulse of specified duration that occurs at a definable time. The
pulse on-time can be varied between 2ms
and 130s in increments of 2ms. If a new ON
command (i.e. trigger) is given during the ON
period the pulse will restart. If a new pulse
width is supplied during the ON period, it
will not take effect until the next ON period.
A pulse can experience a small amount of
time dither that depends upon the amount of
Railbus activity. This can be ± 1% of the pulse
width or ± 3.5 ms, whichever is the longer.
Continuous Pulse (see Notes 2, 3 & 4)
This type of output provides a continuous
pulse train that is defined by the pulse ontime,
and the pulse period (the time between the
start of each ON time). The pulse period is
configurable to any value between 4 ms and
130,000 ms in 2 ms steps. The pulse on-time
is the same as for the momentary action
described above. The on-time must not
exceed the setting for the pulse period. (See
also the above note regarding AC modules.)
Pulses can experience a small amount of
time dither that depends upon the amount of
Railbus activity. This can be ± 1% of the pulse
period, or ± 3.5 ms, whichever is the longer.
Continuous pulse operation has two distinct
modes—static and dynamic. When in static
mode, the pulse parameters are cleared
from memory when the channel is made

inactive; in dynamic mode the values are
retained for use when the channel is made
active once again.
Line Fault detection (2/1 only)
When enabled, this will cause a flag to be set
to indicate a short or open circuit fault even
when channel output is in OFF state.
MODULE OPERATING STATES
Failsafe mode
The module supports failsafe mode as
defined in the earlier I/O module introductory
section, with the following two additions:
1) Channel using “Configured
failsafe values”
In this mode, the module will force the
outputs to predefined levels— defined on
a per channel basis.
On entering “failsafe”:
a) If channel is in Static mode of operation: Pulse mode is disabled and the
channel is configured as a latched
output and is driven to its failsafe
value.
b) If channel is in Dynamic mode of
operation: If in single pulse (momentary) mode, the configuration is not
cleared, but the output is driven to its
failsafe value.
On leaving failsafe:
Channel will adopt the mode defined
below for a channel going from inactive
to active state
2) Channel using “Hold last value”
If the module goes into failsafe during a
single pulse, it is allowed to complete the
pulse before adopting the failsafe state. A
latched (discrete) output will remain at its
current value.