Re: Apple //e's inverted screen?

["Bryan Parkoff" <nospam@nospam.com>]

"David Wilson" <mcs6502@gmail.com> wrote in message 
1159681505.287407.171780@m7g2000cwm.googlegroups.com">news:1159681505.287407.171780@m7g2000cwm.googlegroups.com...
> Bryan Parkoff wrote:
>> Is there a possibility that Apple //e's screen will have white border
>> including left, right, top, and bottom margin on NTSC monitor?  Bit 
>> stream
>> is always inverted before it is shifted out to the NTSC monitor.  If you
>> bring ALTVID signal to high, it would block the inversion while it 
>> continues
>> to shift out without being inverted.
>>     I assume that 16 colors are inverted.
>
> ALTVID' (aux slot pin 27) has a pull up resistor so making it high is
> already the default.
> If you assert it (logic 0) then the screen will be white. It does not
> block the inversion (C5 is a NAND gate operating as an OR gate with
> inverted inputs and not an XOR gate).
>
> If you take ENVID' (aux-29) high (it has a pull down resistor) the
> outputs from the chargen will be disabled and pulled high by RP3
> resulting in black.
>

David,

    Okay, lets say if ALTVID' has low signal.  Will the screen be inverted 
including inverted 16 colors?  Will it show white border in the top, bottom, 
left, and right margin?  Is it possible to wire ALTVID's pin to AN2.  I 
would leave ENVID signal alone.

Bryan Parkoff