M69030 Asiliant Technologies, M69030 Datasheet - Page 117

• 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

5
4-0
`efmp

Vertical Blanking Start Bit 9
Starting Row Scan Count
69030 Databook
The vertical blanking start is a 10-bit or 12-bit value that specifies the beginning of the
vertical blanking period relative to the beginning of the active display area.
In standard VGA modes, where bit 0 of the I/O Control Register (XR09) is set to 0, the
vertical blanking start is specified with a 10-bit value. The 8 least significant bits of the
vertical blanking start are supplied by bits 7-0 of the Vertical Blanking Start Register (CR15)
and the most and second-most significant bits are supplied by bit 5 of this register (CR09)
and bit 3 of the Overflow Register (CR07), respectively.
In extended modes, where bit 0 of the I/O Control Register (XR09) is set to 1, the vertical
blanking start is specified with a 12-bit value. The 8 least significant bits of this value are
supplied by bits 7-0 of the Vertical Blanking Start Register (CR15), and the 4 most
significant bits are supplied by bits 3-0 of the Extended Vertical Blanking Start Register
(CR33). In extended modes, neither bit 5 of CR09 nor bit 3 of the Overflow Register (CR07)
are used.
This 10-bit or 12-bit value should be programmed to be equal to the number of scanline
from the beginning of the active display area to the beginning of the blanking period. Since
the active display area always starts on the 0th scanline, this number should be equal to
the number of the scanline on which the vertical blanking period begins.
These bits provide all 5 bits of a 5-bit value that specifies the number of scanlines in a
horizontal row of text.
This value should be programmed to be equal to the number of scanlines in a Horizontal
row of text, minus 1.
CRT Controller Registers
Revision 1.3 11/24/99
9-15