M69000 Asiliant Technologies, M69000 Datasheet - Page 91

• Manufacturer Part Number: M69000
• Manufacturer: Asiliant Technologies

Specifications of M69000

• Lead Free Status / Rohs Status: Supplier Unconfirmed

MSR
write at I/O Address 3C2h
read at I/O Address 3CCh
7-6
5
4
&+,36
Sync Output Polarity
7
Sync Output Polarity
Bit 7 controls the polarity of the VSYNC output, while bit 6 performs the same function for the
HSYNC output. For both of these bits, a value of 0 sets the corresponding sync output for positive
polarity, while a value of 1 chooses negative polarity.
The original VGA standard was created at a time pre-dating the onset of multifrequency displays
that examined clock rates or counted pulses to determine resolutions. Therefore, different
combinations of positive and negative polarities on the sync outputs were used to set original VGA
displays to any one of three modes (depicted in the table below). However, over time, numerous
additional resolutions and alternate timings intended to improve upon the original VGA standard
came to be widely used. In order to maintain compatibility with the VGA standard, the vast majority
of these use HSYNC and VSYNC outputs that are both configured to be of positive polarity since
this was the only choice left over as ‘reserved’ in the original VGA standard.
Odd/Even Page Select
0: Selects the lower 64KB page.
1: Selects the upper 64KB page.
Selects between two 64KB pages of frame buffer memory during standard VGA odd/even modes
(modes 0h through 5h). Bit 1 of register GR06 can also program this bit in other modes.
Reserved
This bit returns the value of 0 when read.
69000 Databook
(00)
Miscellaneous Output Register
7 6
0 0
0 1
1 0
1 1
Bit
6
negative
negative
Polarity
VSYNC
positive
positive
Output
Page Select
(0)
5
General Control and Status Registers
negative For standard VGA modes with 400 scanlines.
negative For standard VGA modes with 480 scanlines.
Polarity
HSYNC
positive
positive
Subject to Change Without Notice
Output
Reserved
(0)
Vertical Resolution Selected
Not used for standard VGA modes. Often used
for extended modes regardless of the number of
scanlines.
For standard VGA modes with 350 scanlines.
4
3
Clock Select
(00)
2
RAM Enable
(0)
Revision 1.3 8/31/98
1
I/O Address
(0)
0
8-5