Re: Help with Super Serial Card & Obtaining ProDos

[dempson@actrix.gen.nz (David Empson)]

Linards Ticmanis <ticmanis@coli.uni-sb.de> wrote:

> Will Kranz wrote:
> 
> > You guys said things about firmware on the card at $Cx00
> > and using <CTRL-I> or <CTRL-A> (depending on modem/terminal
> > jumper) to change baud rate.

The default control character prefix is actually controlled by a DIP
switch which determines the operation mode (printer is Ctrl-I,
communication is Ctrl-A).  The modem/terminal jumper simply rewires the
DB-25.

> > Any more hints about this? Are there other command options?

Heaps.  Hopefully this is covered in the FAQ for comp.sys.apple2.

> > Does this only work after addressing card with IN#?
> 
> Yes. You need to give IN# first.
> 
> > If 6B is 300 baud, what other
> > rates can one set with what codes?

The usable values range from 1 to 15, and are in ascending order of baud
rate.

1   50
2   75
3   110
4   134.5
5   150
6   300
7   600
8   1200
9   1800
10  2400
11  3600
12  4800
13  7200
14  9600
15  19200

> > I found several articles about the dip switch settings,
> > but nothing on these firmware features.  I tested the card
> > setting baud rate with the dip switches, and it always seems
> > to send 7 bit data with the high bit set even though I say no
> > parity via dips.
> 
> Apple BASIC does this internally AFAIK, it always sets bit 7. Sending
> bytes from machine language should get you around this.

Correct.  Everything output by the PRINT statement in Applesoft has bit
7 set.  The monitor's low-level character output functions have no such
restriction.

> > And how should I have the interrupt enable switch set for use via the
> > operating system, ie IN#.  It seems to work the same way independant of
> > how I have this set, so I just don't get it.  Any help appreciated.
> 
> If you want to use comm programs that do interrupt handling, and if you
> want to use them at high baud rates, set it to "on". The Apple ROMs up
> to and including the unenhanced //e don't do much in the way of
> interrupt handling.

You have to be rather careful with the interrupt enable DIP switch on
the SSC.  If it is enabled, and the CPU has interrupts enabled, and the
SSC is activated, then any change of state on the DSR or DCD flow
control input is sufficient to trigger an interrupt.  If you haven't set
up an interrupt handler, the computer will crash.

In summary: unless you are using dedicated comms software which has an
interrupt handler, you should disable interrupts on the card.

-- 
David Empson
dempson@actrix.gen.nz