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From: val on 31 Mar 2008 17:55
On 22 fév, 01:42, Claudio Lapilli <pleasedonts...(a)isp.com> wrote:
> On Feb 21, 6:17 pm, val <vlep...(a)aol.com> wrote:
>
> > Hello all,
>
> > I would like to build a card for the HP48. It requires that
> > informations are exchanged between the card and the calculator via
> > port 1 or 2. I have limited knowledge in asm and never made a program
> > that use port 1 or 2. Ideally I would like to use a pin of one of the
> > port to transfer data to the card and another one to receive data, and
> > finally a third one as clock (SPI interface to a SD card in fact). Is
> > this possible ? I have looked to hpcalc and in the web but failed to
> > retrieve information on this.
>
> > Any help will be greatly appreciated !
>
> > val
>
> I'm no expert in electronics but I'm not sure what you want is
> possible (from the hardware point of view).
> And even if it was, the speed of the processor is probably not enough
> to initialize an SD card. Minimum clock frequency for communication I
> believe is 600 kHz for an SD card, even the best Saturn assembler
> programmer can't write software to send data with a 600 kHz clock. The
> Saturn works at 4 Mhz, and each instruction takes like 3 to 18
> cycles... forget it.
>
> If you really want to add an SD interface to an HP48, I suggest you
> buy an HP50G!!.
> That's the best help I can offer.
>
> Regards,
> Claudio

Hi,

One may use SD cards in SPI mode and this way there is no problems on
communication speed (you set it using your dedicated clock line). My
problem is more on finding a way to access directly the port 1 or 2
pins to build the communication interface. I have a dead ram card that
I want to use for this purpose. The SD card will be attached to a few
pins of this ram card and the hp48 will talk to the SD card using pins
of port 1 or 2, depending where I plug the card.
If you want to write directly to memory in port 0 you may write, in
asm :
LC(2) XXh
D0=(5)Adr
DAT0=C , or smthg approaching.
But what if the address is supposed to correspond to port 1 (or 2).
I guess that in this latter case there is another way of writing in
external memory. Do we have to use CONFIG, IN, OUT,...?
Basically, does somebody know a way to physically assert/read pins on
port 1 or 2, and which pins must be asserted in order to fake a valid
card (CD, CE, and such).
In fact any info on the way a hp48 reads/writes from or to a ram card
will be helpful to me.

Thanks for your help.

val
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