ABB Symphony Harmony Series, Instruction, Page: 135 / 402

3 - 6 WBPEEUI240751C0
I/O Block
An I/O block that supports digital outputs receives boolean
logic states (0 or 1) from the Harmony controller and converts
them to digital voltages to switch the output channels.
The DOT-120 output channels are fused and monitored
through readback circuitry on the block. The block constantly
monitors readback from the output contacts to verify and
insure hardware and field wiring integrity. The block also
reports the readback values to the controller.
I/O Block
An I/O block interfaces and processes field device input and
output signals. An I/O module mounted on a termination base
forms an I/O block (Fig.
3-5 ). The I/O module contains the
electronics. It handles the Hnet communication and stores
and executes a portion of the process configuration. In general,
a base is a passive device that connects and distributes signals
between the I/O module and field wiring terminals and
between redundant I/O modules.
There are several different I/O block types available (refer to
Table
1-1 ). The three basic types being analog (A), digital (D),
and control (C). All share the same housing layout and connec-
tion, configuration, and mounting methods. Refer to Table
1-2
for a summary of I/O block capabilities.
The front panel of an I/O block communicates a considerable
amount of information including block type, operating mode,
and operating status. Front panel features include:
•
Text-based front panel mode and status indicators.
•
Front accessed power fuses with status indicators.
•
Front accessed stop/reset button.
•
Front mounted device ID and user label area protected by a
clear plastic cover.
Refer to
I/O Block I/O Block I/O Block I/O Block
in Section 7 for further explanation of front
panel items.