M69030 Asiliant Technologies, M69030 Datasheet - Page 90

• Manufacturer Part Number: M69030
• Manufacturer: Asiliant Technologies

Specifications of M69030

• Operating Temperature (min): 0C
• Operating Temperature Classification: Commercial
• Operating Temperature (max): 70C
• Rad Hardened: No
• Lead Free Status / Rohs Status: Supplier Unconfirmed

8-2
ST00
read-only at I/O Address 3C2h
partially shared and partially shadowed between both pipelines A and B as shown
7
6-5
4
3-0
`efmp
A
B
Ret Interrupt
Ret Interrupt
PIpe A Vert
PIpe B Vert

Vertical Retrace Interrupt
Reserved
DAC CRT Sense
Reserved
69030 Databook
7
Input Status Register 0
0: Indicates that a vertical retrace interrupt is not pending.
1: Indicates that a vertical retrace interrupt is pending.
Note: This bit does NOT indicate the status of any real hardware interrupt occurring at the
onset of vertical retrace. This bit works in conjunction with bit 3 of ST01 and bits 4 and 5
of CR11 to implement a “phantom” interrupt for the sake of compatibility with older software.
Early VGA graphics systems (and their predecessors, including the EGA) had the ability to
generate a hardware interrupt on IRQ9 whenever a vertical retrace commenced. This was
done because in these earlier graphics systems it was important for the host CPU to wait
for a vertical retrace interval before accessing the frame buffer. If the host CPU accessed
the frame buffer at a time other than the vertical retrace interval, i.e., while data for the
active display area was being drawn to the display, then either “snow” on the display or a
flickering display would result. Later graphics systems, including this one, do NOT actually
generate this interrupt.
These bits return the value of 0 when read.
Indicates the state of the DAC analog output comparators. The comparators can be used
to determine whether a CRT is currently attached, and/or whether the CRT is color or
monochrome. This is done by blanking the CRT outputs, which causes the color value
stored at index 0 in the color lookup table of the RAMDAC to be continuously output to the
CRT. Different color values can then be written to the color lookup table at index 0 to set
different output levels for the red, green and blue D-to-A converters.
These bits return the value of 0 when read.
Result
0
1
6
Reserved
When Testing for Presence of CRT
General Control and Status Registers
5
No CRT is present.
CRT is present.
DAC CRT
Sense
4
3
2
When Testing for Color or
Reserved
Monochrome CRT
Monochrome CRT.
Color CRT.
Revision 1.3 11/24/99
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