[Coco] Re: Re: [Color Computer] Re: Adapter from Coo3 to SVGA

[Rodney V Hamilton]

In article <42512D8A.18685.C5802A at localhost>, 
jdaggett at gate.net said...
>
>Torsten
>
>Yes pin#10 from  the monitor connector goes to PB3 of IC4 
>(68B21). PB4 to PB7 of that chip is also not used!!!
>
>These four pins can be used for a SPI, I2C, PWM, or general 
>purpose I/O. These were the mode control pins that were used on 
>the Coco1 and Coco2. Only the Coco3 can use these pins for other 
>purposes. 
>
>PB3 to PB7 is not mirrored inside the GIME. 
>
>james

Are you sure about that, James?

You don't normally see it, but the GIME emulates the 6847T1 chip
and uses these bits to control the "extra" display features.  If
you change the control mask at &H95C9 from 7 to 255, you can see
the effect of these bits.  BASIC normally masks them off when it
returns to the OK prompt.

Here is what they control in the GIME:
  ff22.3  CSS  color set select (try SCREEN 0,1)
  ff22.4  LC   lowercase enable
  ff22.5  INV  inverted video enable
  ff22.6  BRD  border color enable
  ff22.7  GFX  graphics mode enable

Normally, you would use a mask of 127 so that the screen
always returns to text mode when the program exits.

Rodney