
TD040300-0MF
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words, but in the Modbus application protocol they are sent as two-byte transfers.
However, the input data registers for each I/O point are represented as 32-bit registers
regardless if they represent an analog or digital point. On input registers, the least
significant word occupies the odd address while the most significant word occupies the
even address. Output data registers require only one register per point. What follows
are the register locations for universal I/O points 1–6 and for relay outputs 7 and 8.
Table 2 — Register Mapping for Input/Output Channels 1–8
7.4.1.1 Status Registers
Each of the eight BAS Remote I/O points has one 16-bit status register. Register
location 40001 corresponds to channel 1 while register 40008 corresponds to channel
8. The value of the status register depends upon how the I/O point is configured. For
example, an out-of-range indication only applies to those channels configured for
thermistor inputs. A similar situation applies to analog voltage outputs and analog
voltage inputs. All channels operating within their limits will report a 0x00 when reading
the lower 8-bits of the status register.
Channel operating within limits
Analog current output has no load
Thermistor value out of range
Analog output deviates by ±60 mV
Channel is in automatic operation
Channel value is being overridden
Table 3 — Status Registers
Figure 45 — Status Register Depicted Graphically
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