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From: meghas@hpcvra.CV.HP.COM (Megha Shyam)
Newsgroups: comp.sys.handhelds
Subject: Re: HP48 Serial Interface Pins
Message-ID: <21580088@hpcvra.CV.HP.COM>
Date: 4 May 90 22:08:58 GMT
References: <128rhelps@yoda.byu.edu>
Organization: Hewlett-Packard Co., Corvallis, OR, USA
Lines: 45

/ hpcvra:comp.sys.handhelds / rhelps@yoda.byu.edu /  6:00 pm  Apr 22, 1990 /
>I am looking for the pinouts for the serial interface on the HP48sx

>The suppserial cables from HP seems no more than a trickle at present. For
>those adventurous souls that want to do it themselves here is a repeat of my
>earlier message on pinouts.

>Pin numbering. Lay the calculator on the table, look into the port and number
.1-4 from left to right. 4 is closest to the IR leds.
.IBM AT 9 pin plug HP plug
>2 (Rx) 2
>3 (Tx) 3
>5 (Gnd) 4
>--- 1 (Chassis ground ??)
>You may also want to short out pins 1-6-7-8 on the IBM side to keep its
>handshaking satisfied. See other notes on this net for suggestions for a plug
>to go into the HP.

>Request to HP: We are all eagerly looking out for accessories such as the
>Programmers Reference Manual and the engineering formula ROM card. Don't keep
>us hanging on too long. RAM cards have arrived but the price is daunting.
>With the current price of RAM chips for PCs does your special packaging really
>justify $250 for 128K?

>- Richard Helps -
>BYU, Provo, Utah. All the usual disclaimers and please be careful when
>handling your calculator hardware.


Comparing RAM prices for PCs and deducing the price for the HP 48SX RAM card
is like comparing apples and oranges; PC almost exclusively use dynamic RAMS
which are of course very cheap; HP 48SX needs and uses static RAMS which are 
much more expensive.  Part of the reason is one bit of a static RAM has 6
transistors while i bit of a dynamic RAM has one transistor. 

Static RAM density has not reached the DRAM density level and will probably 
never compete in price.  The other issue to consider is that the RAM card 
should be considered as a system which meets HP 48 electrical specifications
which is quite different that the standard 5 +/- .5 V specification.  All
these add to cost of the manufacture of a card.  

I hope that this clarifies the situation.

Megha Shyam
Hewlett-Packard