Help on N80C51BH Programming

[Hugoneus]

Hi all,

Does anyone have any experience with this part? Do you know of an equivalent part? I am trying to find a way to program one of these and so far no luck.

Thanks everyone,

[wraper]

You need some parallel programmer which supports it (Edit, for intel 87C51 and most of clones with eprom or flash, as said in the next post 80C51 has a mask ROM). You could use Atmel AT89S51 instead. It can be programmed with the same cheap isp programmers as AVR microcontrollers. Simplest is just few wires from LPT port + 5V power. There must be crystal or external clock source connected too unlike with AVR.

[free_electron]

the 80 version is mask rom
80x51 = mask rom
83x51 = otp
87x51 = uv eprom
89x51 = flash

[Hugoneus]

Thank you both,

That is what I was afraid of... This chip belongs to a display driver for an Agilent power supply. The whole display was dead, including this IC. Unfortunately, I can't replace it, because I don't have one which has the initial code on it.

I am almost done shooting this video and I wanted to know if it is even possible to find a replacement.

[Hugoneus]

Hey free_electron,

Do you happen to have any information on the Agilent E364xA power supply displays? This is where this component is from.

Thanks,

[free_electron]

i've seen bad display boards before on similar supplies.

check a few things wil ya ( unless there is an obvious crater in that chip )

- see if the cpu clock runs.
- chekc the level of the reset pin

be VERY careful when prodding around in these display boards ! there is the 20 volts rail for the VFD and the 3.3 volts ac for the filament. that whole stuff is level shifted 18 volts above the normal ground level for the digital logic on the main board. This is true for ANY VFD style board in any agilent equipment !

don't make the mistake to pick ground at the chassis and prod around in the display board, one slip of the probe and you fry the damn thing !

things i know happen to these boards and are frequently the cause for thinking the board is dead or the cpu is broken ( i have never known the cpu to die )

- no clock due to bad crystal
- cpu held in reset due to broken level shifters (LM339's are used to level shift the 18 volt signals into the local 'lifted' 5 volt domain )
- absence of the 3 votl AC for the filament
- shorted 0.1 uf caps.  check if the power rail isn't shunted...
- the resistors around the level shifting network going bad. if you find brownish resistor with yellow legend : warning ! those fuckers grow dendrites and go bad. i;ve sene those go off in the ADC section of 3631 taking out the OP711 and OP706 opamps along the way.
- the VFD drivers having a broken chain ( this is frequently when multiple segments appear 'shorted' but it can also lead to a complete display being off.  the VFD drivers were originally TI chips but they went obsolete. they are still manufactured by supertex and are essentially simple 32 bit shift registers with high voltage outputs.

the only vfd controllers i know off that can really die are the old upd75xxx based ones. but agilent discontinued those very quickly. that upd75 is a cpu with on board vfd drivers and they were running that at the limit... those things died in droves. they switched to an 8051 with the TI drivers that are specced at 30 volts.

if you can get me the markings on the label stuck on the cpu i can check if i can get the programmed cpu. sometimes they are available. they may even be identical between multiple machines but i need the hp number xxxx-xxxx on the little yellow label. (sometimes engraved under the 8051 marking also, no label then )

agilent uses the same setup in multiple machines . that is why they can afford to buy that stuff as mask version. there is no intelligence in that code. it is simply a stream of bytes holding the digit information and single bit  annunciators ( like the ERR , ON , -5v fixed texts ). the host software on the motherboard does the work. the 8051 only does the display scanning. there is no processing in there. the 8051 also scans the keyboard matrix and simply reports two bytes back. one control byte and one holding the number of the key pressed. again the mapping is done in the host processor.

i have several frontpanels of BER machines. if you are lucky there is one in there with the same mask code.

[Hugoneus]

Dear free_electron,

Thanks a lot for the detailed response. I actually have already shot the video and have done pretty much all that you have suggested. The video will appear soon. If I can buy a part from you that would be great!

If you have the time, please take a look at the video when it finishes processing and let me know.

Cheers,

- Shahriar

[free_electron]

i quickly scrolled the video : as i suspected : see the marking 34401-88804 rev 01 ? on the 8051

that s the same guy as in the 34401 multimeter. or the 3490a mux. i have frontpanels from those.

error 601 means the display does not shift out data to the main board.

you definitley have a crater on the 8051 . it looks like the supertex display driver fried out and injected the 20 volt intot the 5 volt rail. most likely all the chips are fried.

that 5 volt regulator will be shot , so will be the 299 and the other stuff. i'll find you an entire front that has enough  parts so you can swap it entirely. i may actually have one from these short stack power supplies. all you may have to do is swap out the vfd to get the correct annunciators. i'll dig around in my lab tomorrow evening.

the 36 volts at the output you see is the vfd rail + the 18 volt shift between ground of the front panel board and ground of the . eh. how to explain thsi thing...

the 7805 makes a voltage that should be 5 volts BELOW the 36 volts rail.. it now hangs at 18 volts below the 36 volt rail.. thats a definately dead...

so the supertex flashed over and sent the 18v rail into the 5 volt ground basically putting 18 volt across the 5 volt circuitry.
the regulator is shot and the supertex was feeding it 18 volt ...

that thing is a simple 7805 in so-8

if you need the schematic for that front panel search in the service manuals for similar supplies like the 66311 supplies. it'll be the same. or any other half size brick supply with vfd's

that will show you how the 5 volt rails hangs under the 36 volt top .

[adriten]

hello free_electron,
do you happen to have a 34401-88804  for sale ?   I'm stuck with my E3634A power supply and the problem is a failed  80C51   
Thanks in advance
adri