[Coco] V.PAGE

[L. Curtis Boyle]

On Mon, 21 Jul 2008 10:48:02 -0600, Robert Gault  
<robert.gault at worldnet.att.net> wrote:
>
> You only probe once, curing the init phase of the driver. That uses an  
> insignificant amount of processor time.
>
> If you are going to create a system with multiple RS-232 cards or disk  
> controllers, you will need to also create custom drivers as none of the  
> current ones are designed this way.
> As I said, if this is just for you then modify OS-9 to your hearts  
> content. :)
>
> Auto-probing is not dangerous if done with correct coding. Obviously one  
> turns off interrupts before switching the MPI, uses the intended device,  
> and resets the system as it was found when the driver gets finished.  
> This is exactly what a driver must do if not the floppy controller.
> Study the NitrOS-9 code for examples.
>
     That may be true for disk controllers, but RS-232 does allow multiple  
cards (the Comm-4 board from Alpha technologies had 4 ports, as an  
example). The device descriptor determines it by the address of the card,  
and each get's their own buffer (especially if using SACIA for 6551 based  
ports, and DACIA for 6552 based ports). When we used to run the Coco  
3/Nitros9 system here at work, we had 3 parallel ports, and 8 serial ports  
(4 6551, 4 6552 (2 ports per chip on the latter), and we drove 8 ADM  
terminals from those.

-- 
L. Curtis Boyle