DESCRIPTION AND OPERATION
MODULE BLOCK DIAGRAM
2 - 2
WBPEEUI240754A0
®
Default data from the control module is sent to the default reg-
ister. The control module configuration sets the default values
(Function Code 128). The default register is reset to logic zeros
during power up to drive the outputs to a de-energized state.
FC 128 in the control module configuration selects the output
values used to drive the output circuits in the event of a con-
trol module failure (
time-out
). If FC 128 is not defined, the out-
puts will go to a de-energized state during a
time-out
. Refer to
in this section for further explanation of
time-out.
The default control logic block is a one bit latch register. It
sends a signal to the data selector block to select either the
default register data or the output register data during a
time-out
(indicating a control module error). This signal is
dependent on the control module configuration (FC 83 specifi-
cation S2). The bus fault detector in the I/O expander bus
interface checks for a
time-out
condition. During a
time-out
, the
data selector block normally selects the default register data. If
a
hold
option is selected in FC 83, the default control logic cir-
cuits send a logic 1 to override the data selector. It causes the
data selector to drive the outputs with the output register data
instead of default data to maintain the outputs at their current
values (
hold
).
Status Logic
The status buffer block provides module status information to
the control module. This information is output states, and
module identification and status. The control module reads
this data through the I/O expander bus interface. Refer to
Out-
put Control Logic
in this section for an explanation of the
data.
Figure 2-1. Block Diagram
LOGIC
POWER
RELAY
POWER
CONTACT
OUTPUTS
I/O
EXPANDER
BUS
TP80659A
I/O EXPANDER
BUS
INTERFACE
BUS FAULT
DETECTOR
MODULE
STATUS
DATA
SELECTOR
STATUS
BUFFER
DEFAULT
CONTROL
LOGIC
OUTPUT
REGISTER
DEFAULT
REGISTER
P2
P3
P1
ADDRESS SWITCH
MODULE
STATUS LEDs
RELAY
DRIVER
RELAYS
1
8
OPEN
S1
OUTPUT
STATUS
LEDs
