Re: [cc65] RS232 question

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From: Robert Steinmetz (
Date: 2003-04-12 19:04:46

Ullrich von Bassewitz wrote:

>I've had a first look today on how to redesign the RS232 routines when
>converting the drivers to loadable modules. Two questions I'm undecided about
>  1. Would it make sense to support more than one serial port?
Yes Apple //c and //gs have 2 ports.

>  2. If so, would it make sense to allow different drivers for the ports?
This would be desirable for Apple IIs, as it is possible to have 
different serial ports in different slots. I'm not sure but internal 
modem cards may need a from of serial prot software and there may be a 
serial port card for printers. Parallel Ports cards may be similar as well.

>1. has some overhead, because a port number must be passed to several
>routines, 2. has even more overhead, because the different ports must be
>handled in the rs232 kernel functions (outside the drivers). Mixing the two
>options (say: port #1 and #2 are handled by driver #1, while port #3 is
>handled by driver #2) is so complex that I would say it's not worth the
In the Apple II world at least hardware accelerators are common. As are 
smart serial cards, which significantly reduce the load on the main system

>My approach would be to handle just one port as it is now (the 6502 has
>difficulties handling even one port with decent baud rates), but since I'm
>about to do a redesign on the API level, I thought I'd better ask...
>Comments anyone?
>        Uz
Rob Steinmetz

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