M69000 Asiliant Technologies, M69000 Datasheet - Page 107

• Manufacturer Part Number: M69000
• Manufacturer: Asiliant Technologies

Specifications of M69000

• Lead Free Status / Rohs Status: Supplier Unconfirmed

9-14
5
4-0
&+,36
Vertical Blanking Start Bit 9
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.
Starting Row Scan Count
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.
69000 Databook
Subject to Change Without Notice
CRT Controller Registers
Revision 1.3 8/31/98