Technical Description
Port C relative addressing (when port C is split)
The input and output nibbles will each be treated as individual four bit ports.
Port Configuration:
Each
Note: : The control panel also allows you to configure the device. Your program can over ride the control panel configuration when executed, but the control panel configuration will be the default on power up. The default settings are based on the settings in the control panel application when last changed and saved after re
Control Word 0: Bank 1 (A1, B1, C1)
Control Word 1: Bank 2 (A2, B2, C2)
Control Words
I/O Configuration
CWnD0 | Port C1 lower nibble (bits |
| 1 = input |
| 0 = output | 1 on power up |
CWnD1 | Port B1 |
| 1 = input |
| 0 = output | 1 on power up |
CWnD2 |
| 0 or 1 (no effect) |
|
| ||
CWnD3 | Port C1 upper nibble (bits |
| 1 = input |
| 0 = output | 1 on power up |
CWnD4 | Port A1 |
| 1 = input |
| 0 = output | 1 on power up |
CWnD5 |
| 0 or 1 (no effect) |
|
| ||
CWnD6 |
| 0 or 1 (no effect) |
|
| ||
CWnD7 |
|
| Always a 1 |
|
| |
Figure 4-Control Words
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. With a Port argument of 0 and an API function meant to output data, the first (0th) output port on the device will be utilized. Likewise, with a Port argument of 0 and an API function designed to input data, the first (0th) input port of the device will be utilized.
In all addressing modes, port numbers are zero
Page 9 |
