Bochs VBE Extensions: Difference between revisions
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== Programming the BGA == |
== Programming the BGA == |
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=== Writing values === |
=== Writing values === |
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To write an index/data pair to the BGA, |
To write an index/data pair to the BGA, first write the index value to the 16-bit IO-port VBE_DISPI_IOPORT_INDEX (0x01CE), followed by writing the data value to the 16-bit IO-port VBE_DISPI_IOPORT_DATA (0x01CF). The BGA supports 10 different index values (0 through 9): |
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* VBE_DISPI_INDEX_ID (0) |
* VBE_DISPI_INDEX_ID (0) |
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* VBE_DISPI_INDEX_XRES (1) |
* VBE_DISPI_INDEX_XRES (1) |
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In order to change any of the registers (with the logical exception of VBE_DISPI_INDEX_ENABLE), the VBE extensions must be disabled first. To do so, write the value VBE_DISPI_DISABLED (0x00) to VBE_DISPI_INDEX_ENABLE (4). The changes are not visible until the VBE extensions are enabled again. To do so, write the value VBE_DISPI_ENABLED (0x01) to the same register (see also note below on enabling the LFB). |
In order to change any of the registers (with the logical exception of VBE_DISPI_INDEX_ENABLE), the VBE extensions must be disabled first. To do so, write the value VBE_DISPI_DISABLED (0x00) to VBE_DISPI_INDEX_ENABLE (4). The changes are not visible until the VBE extensions are enabled again. To do so, write the value VBE_DISPI_ENABLED (0x01) to the same register (see also note below on enabling the LFB). |
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TODO: check whether we can read registers as well, and describe |
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