>I believe that SC meant "Standard Cell". That would make the
>87157 just another part number, between the 87156 and 87158.
>The "P" probably meant a 40 pin DIP package.

ACK to the meaning of "SC" and "P" within "SC87152P".

>Toward the end of the color computer, Tandy made a number of
>ASICs with Motorola (now Freescale) to cut costs.

That's true, but it looks like the trackball is a 3rd party device from WICO.

>At the time, Motorola was fighting Intel with the 68000 versus
>the 8086, and with the 68HC11 vs the 80C51. It is unlikely that
>they would cooperate with an 87C152 second source.

Sounds logically. This took me aback too.

I'll analyze the circuit now. Maybe this will exclude the 87C152 from the design.

Thanks & regards,
Torsten