The Museum of HP Calculators

HP Forum Archive 06

[ Return to Index | Top of Index ]

HP11C+ ?????
Message #1 Posted by Vieira, Luiz C. (Brazil) on 12 Sept 2001, 12:43 p.m.

About 10 years are past since my (at that time) recently bought HP16C lost two columns of operating keys. They were <D> to <STO> and <0> to <7> columns. I opened the calculator and could see that the 10 Series keyboard is, in fact, a 8X5 instead of a 4X10 matrix (1 control line less?), with folded, symmetrical columns. My 16C is the one with a complete, all on board PCB, no flex print for the display and ICīs. I tracked all PCB and I figured out that the keyboard scanner IC (don’t remember the ID #) was faulty, not the kbd PCB. I had also a broken HP11C that I latter used to trade for a new HP32S with Hewlett Packard, in a time HP bought our old models as we bought their new ones (at least here, in Brazil, late in 1980īs; in fact, they may have a lot of them to offer at eBay...). I could see that the KBD scanner was common at least to the HP11C, 15C and 16C. Next? Well, I simply removed the 11Cīs KBD scanner and replaced the faulty 16Cīs for that. The 16C is working fine, thanks.

One fact that called my attention was that the 15C had 3 ICīs against the only two of the 16C ad 11C. I concluded that the 15Cīs extra IC was for the extra 64 registers. The display controller was different for each of them, so the scanner itself would in fact be the CPU, and the display driver would contain the O.S. for each model. Is it correct?

The point is that some months before that I could see and even use an HP11C that could reach more than 440 (448 max?) program lines!!! The owner told me he bought it from someone that worked at Hewlett Packard (Brazil) and it had been modified in USA. He told me, at that time, that only one IC was added.

My HP16C has space and soldering-pads for a PQPF at the same position the 15C has the extra IC. The question is: have someone did (or knows about) something like this?

If not, I am the witness of the existence of, at least, one freaky 448+ HP11C.

Re: HP11C+ ?????
Message #2 Posted by Tony Duell (UK) on 12 Sept 2001, 2:15 p.m.,
in response to message #1 by Vieira, Luiz C. (Brazil)

The original Voyagers contained 2 chips. The smaller one is a Nut CPU (similar to the CPU in the HP41 -- the data sheet gives the differences, mostly to do with voltage levels). As in the HP41, it contains the keyboard scanning logic. The larger chip is called R2D2 (ROM/RAM/Display Driver) [Seriously], and is what it says it is. As it contains the ROM, it is machine-specific. I'd always assumed that the third chip in the 15C was ROM/RAM, but I have no definite proof of this. I have no idea if an 11C will recognise the extra RAM if it is added -- and I don't have the parts to try it. Incidentally, I've found a lot of dry joints in Voyagers (of all types) -- if you get one with missing keyboard rows/columns or missing display segments, or even one that won't work at all, then try resoldering both chips. I've brought several back to life that way.

Re: HP11C+ ?????
Message #3 Posted by Vieira, Luiz C. on 12 Sept 2001, 3:33 p.m.,
in response to message #2 by Tony Duell (UK)

Well... You got to the point.

If R2D2 (did G.Lucas copyright it?) is ROM/RAM/Display Driver, it can be configured so (production line, I mean) it has as many ROM or RAM as needed, right? The HP15C has three fixed registers: I, 0 and 1 (matrix indexes and indirect index). All others can be converted to program lines.

The HP11C is differently organized. Only I register is fixed; all others can be converted to program lines, being 63 the minimum available space for programs. There is no register beyond R.9 (R19) on the HP11C. The HP15C, for natural reasons, access registers till R65 by using Index register.

My question is: would the ROM space be increased to accomplish new advanced features directly inside R2D2? By keeping the 11C structure, a remap for the keyboard would take place to add new codes and new features. As the 10C and 12C have different memory maps than the 11C itself (the HP16C is closer to the HP11C), they have their own internals for the R2D2.

I believe one single experience would allow us to get there: remove the third IC form one available 15C and switch it on. If everything works fine and memory is restricted to registers I, 0 and 1, the third chip contains the 448 bytes. In other hand, no advanced function can be tested neither a program can be written, cause there is no memory to do so. Another point is that reset condition expects registers till R.9 (R19). Maybe this would not allow the system to start up.

A lot of questions... and no practical result. Besides that, only someone having all answers could help. People at HP? Would they give a hint?

Re: HP11C+ ?????
Message #4 Posted by Tony Duell (UK) on 12 Sept 2001, 5:15 p.m.,
in response to message #3 by Vieira, Luiz C.

My guess is that, like the HP41 (also NUT-based), there is no electronic difference between RAM used as data registers and RAM used for programs. The partitioning is entirely done in software. So the different memory layout between various Voyagers is irrelevant at the moment. Also, I suspect that all the R2D2 chips contain the same amount of ROM and the same amount of RAM (maybe the 10C one contains less), and that the extra chip in the 15C (which may actually be similar to an R2D2 with the display driver section disabled or not used) cotnains both the extra ROM (for the extra functions) and the extra RAM. The keyboard layout, again, is determined by software. The 15C has the same number of keys as the other Voyagers, so the keyboard scanning hardware (in the Nut) is the same. I don't have a 15C (at all), so I can't desolder the extra chip and see what happens.

[ Return to Index | Top of Index ]

Go back to the main exhibit hall