HP1350 Graphics Translators

From: Bob Shannon <bshannon_at_tiac.net>
Date: Sat Jun 14 14:45:01 2003

The HP 1350A has two 10-bit digital to analog converters that appear to
drive an analog vector generator that is
very similar to those used in some of the older vector arcade games.

The memory capacity is 2048 instructions, and each instruction can be a
(light or dark) vector, or a letter or symbol.
All addressing is absolute, and there is no short-vector relative
addressing like an Imlac PDS-1 or VT-11 vector
generator.

The 2048 word memory can be divided up into 'files' that can be
selectivly blanked, cleared or overwritten.

A simple TTL state-machine drives X and Y axis ALU/Accumulators that
feed the discrete transistor-ladder DAC's
for each axis. Some logic looks at the vector lenght and optimises the
writing speed and Z axis intensity, but this is
by far the weakest feature of the device. Some shorter to intermediate
lenght vectors are drawn too brightly, enough to
be noticable.

There are some ROM subroutines that generate letters and symbols, and an
additional socket allows custom symbols
to be displayed with a single-word instuction. There does not appear to
be any form of light-pen input as on the VT-11
and some (optional) Imlac's.

To get a HP 1350 working, you need some coaxial cables and an X/Y
monitor. I've used a HP 1335, as well as some
Tektronic's X/Y monitors (420 and 611). I've found that with the Tek
monitors I can get a perfect X/Y aspect ration by
using a 75 ohm and 50 ohm coaxial terminator for the X and Y axis (using
BNC T fittings). You also need some sort
of HPIB host to drive the thing, although a PIC-based RS-232 adaptor
should be quite easy to design.

The basic 'GTML' language is ASCII-based. You address the device (like
any HPIB listener) and send it strings of commands
and data. A set of LED's on the front pannel will show what context the
data is being read in (commands versus data).

As the commands are read, the HP 1350 will alter its internal memory and
start to draw vectors and symbols.

Lines are drawn with the PA (plot absolute) instruction:

PA(X coordinate),(Y coordinate);(X coordinate),(Y coordinate)

These can be strung together for form complex lines like:

PA0,0;0,100;100,100

And so on.

You control visible versus invisible vectors with the PE (pen enable)
instruction:

PE1, - Pen enabled, draw bright vectors.
PE0, - Pen disabled, draw dark vectors.

Additionally you can enter text mode with the TX instruction:

TXHELLO WORLD!

Will draw 'HELLO WORLD!' on the screen in the current text size and
orientation. Text can be drawn at 4 sizes and in
 two 90-degree rotations. Basic ASCII text formatting functions are
supported like CR, LE, etc.

As with any analog vector generator, the 'quality' of the vector display
directly reflects the finesse of the hardware designers
and the quality of physical construction. Like other simlar HP
equipment the HP 1350 uses top quality components and
the analog design practices used are excellent, so the vectors are sharp
and crisp, with well defined end points. The linearity
of the analog vector circuits is excellent so the lines are very
straight and the end-points match very well.

Physically the HP 1350 is a small 3 1/2 tall rack-mountable box with a
power switch and a few LED's on the front pannel.
Inside one large PCH holds the X and Y axis accumulators and DAC's. Two
smaller logic boards sit below with what
appears to be the control state machine and Z axis logic on one board,
and the HPIB (or optionally serial) I/O board on
the other. The box is about 18 inches deep, but its rather light for
its volume.

I have 2 HP 1350A's and one HP 1351A, but only one of the 1350A's is
operational. Both of the other machines appear
to have power supply problems or are incomplete.

If your HP 1350 powers up and you get the red power interupt light, try
to address it and send it "20,13,10" (decimal)
and it should clear the interupt led and remain in Listen, Command
state. Now its ready to for commands like 'EM' to erase the display
memory and begin drawing vectors.

Being a totally external box, the vector display list does not take up
host CPU memory like the VT-11 or Imlac PDS-1, but
the host also does not have the same instant access to the display list,
a pretty clear distinction between the 1350 and the
other two vectors generators I'm familiar with.

If your looking for a vector display system and you have a HPIB
interface, I'd reccomend the HP 1350 as being quite
easy to get working. I'm not sure I undersand my HPIB protocol problem
just yet, but I'm using very experimental software
so this is not unexpected.


emanuel stiebler wrote:

> Bob Shannon wrote:
>
>> For curious minds not familiar with this device, the HP 1350 is a
>> vector graphics controller with a 1K by 1K addressable
>> display space. Usually they come with a HPIB interface but there
>> was a serial (RS-232) I/O option. The HP 1350 can
>> draw vectors or letters and symbols with a simple ASCII command
>> language (called GTML) and its own internal display
>> list memory, and were often used with older HP calculators and
>> computers such as the HP 1000 line.
>
>
> Can you tell us more about this thing ? I was always fascinated by
> vector sceens (One day, I have to try to build my own controller ;-)
>
> I tried google, but HP decided to make a printer cartridge with that
> number, so no fun there ...
>
> And, probably you have to wait for tony. He has one of this things too
> ;-)
>
> cheers
Received on Sat Jun 14 2003 - 14:45:01 BST