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Technical Description
Relative Addressing vs. Absolute Addressing
The SeaIO API makes a distinction between "absolute" and "relative" addressing modes. In
absolute addressing mode, the Port argument to the API function acts as a simple byte offset
from the base I/O address of the device. For instance, Port #0 refers to the I/O address base + 0;
Port #1 refers to the I/O address base + 1.
Relative addressing mode, on the other hand, refers to input and output ports in a logical fashion.
th
With a Port argument of 0 and an API function meant to output data, the first (0
) output port on
the device will be utilized. Likewise, with a Port argument of 0 and an API function designed to
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input data, the first (0
) input port of the device will be utilized.
In all addressing modes, port numbers are zero-indexed; that is, the first port is port #0, the
second port is #1, the third #2, and so on.
Sealevel Systems PIO-24.PCI
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