ABB Symphony Harmony Series - Page 143

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I/O Block
LED Drivers and Status LEDs
The LED drivers control the front panel status indicators as
directed by the CPU. The indicators show I/O module operat-
ing status, error codes, digital I/O states, and power status.
I/O Channel Interface
The I/O channel interface allows the CPU to select an I/O
channel. For an output channel, the CPU can write control
information to the channel and can acquire readback data and
status. For an input channel, the CPU can read input data and
status from the channel.
NOTE: The block diagram (Fig. 3-7) shows the interface in schematic fashion.
The actual implementation may vary depending on block type; however, the
interface function still applies.
I/O Section
The I/O section varies based on the I/O block capabilities.
Each I/O block is populated with varying numbers and types
of I/O channels. The I/O channel types include:
AI - analog input.
AO - analog output.
DI - digital input.
DO - digital output.
In general, the I/O section circuitry provides:
• Range and mode selection for analog I/O.
• Voltage threshold selection for universal digital inputs.
• Signal buffering.
• Signal conditioning.
• Signal isolation.
• Noise rejection.
• Analog-to-digital and digital-to-analog conversion; one A/D
per channel on AIN-200, AIN-220, and AIN-300.
• Readback of outputs.
• Open and short detection.