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Update expansionportpio.md

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Aric M 2020-07-23 17:11:41 -05:00 committed by GitHub
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@ -4,7 +4,7 @@ bytes would contain the expansion ROM header.<br/>
For region 1, the CPU outputs a chip select signal (CPU Pin 98, /EXP).<br/> For region 1, the CPU outputs a chip select signal (CPU Pin 98, /EXP).<br/>
For region 2, the CPU doesn't produce a chip select signal (the region is For region 2, the CPU doesn't produce a chip select signal (the region is
intended to contain multiple I/O ports, which do require an address decoder intended to contain multiple I/O ports, which require an address decoder
anyways, that address decoder could treat any /RD or /WR with A13=Hi and A23=Hi anyways, that address decoder could treat any /RD or /WR with A13=Hi and A23=Hi
and A22=Lo as access to expansion region 2 (for /WR, A22 may be ignored; and A22=Lo as access to expansion region 2 (for /WR, A22 may be ignored;
assuming that the BIOS is read-only).<br/> assuming that the BIOS is read-only).<br/>