802Ah - Modem I/O BASE Register 0
7 | 6 | 5 |
| 4 | 3 | 2 | 1 | 0 |
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A7 | A6 | A5 |
| A4 | A3 | 0 | 0 | 0 |
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0 | 0 | 0 |
| 0 | 0 | 0 | 0 | 0 |
802Ch - Modem I/O BASE Register 1 |
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7 | 6 | 5 |
| 4 | 3 | 2 | 1 | 0 |
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A15 | A14 | A13 |
| A12 | A11 | A10 | A9 | A8 |
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0 | 0 | 0 |
| 0 | 0 | 0 | 1 | 1 |
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The Modem I/O Base registers determine the base address of the I/O range used to access function specific registers. These registers allow the function's registers to be placed anywhere in the host's I/O space. I/O Base 0 contains the low order byte
Base 0 are always 0. Since only A15 to A4 are decoded by the controller (64K address space), it is up to the host to resolve any conflicts with addressing above 64K.
These registers are still accessable even if the “Enable Base and Limit” bit in the MCOR is cleared (0).
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