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Source: PS/2
Hardware Interface Technical Reference May 1988 (Pages 487-490 physical)
Auxiliary Video Extension Pinout
Auxiliary Video Extension Signal Descriptions
Auxiliary Video Connector
Auxiliary Video Block Diagram
Related Registers
Auxiliary Video Connector (AVE)
The auxiliary video connector is a 20-pin connector located in-line with one
of the channel connectors on the system board. (Ed.
The 8580-Axx planar has *two* AVE slots.)
This connector allows video data to be passed to and from an adapter. The video
buffers can be turned off, and video output from the adapter can be sent
through the video DAC to the display connector. The full channel is available
for use by the adapter. Video output can be passed in only one direction at a
time. The 'dot clock' signal cannot drive both EXTCLK to the VGA and PCLK to
the DAC.
Auxiliary Video Block Diagram
Related Registers
Miscellaneous Output Register - Hex 03CC/03C2 (Page 432 physical)
Bits 3, 2: These two bits select the clock source. The external clock is
driven through the auxiliary video extension. The input clock should be kept
between 14.3 MHz and 28.4 MHz.
Bits
3 2 | Function |
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| 0 0 | Selects 25.175 MHz clock for 640/320 Horizontal PELs |
| 0 1 | Selects 28.322 MHz clock for 720/360 Horizontal PELs |
| 1 0 | Selects External Clock |
| 1 1 | Reserved |
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