View Single Post
Old 5th Oct 2019, 6:16 am   #5
circuitryboy
Pentode
 
circuitryboy's Avatar
 
Join Date: Jun 2012
Location: Bristol, UK.
Posts: 115
Default Re: A Simple Programmer for TESLA "MH74S-" bipolar PROMs

A TESLA version of the SoC PROM Programmer

I built the circuit of SoC PROM blower way back and I have a Much Modified MK14 to drive it.
And TESLA document shows the same 10V5 Vccp that the "DM" chip requires.
So amending the SoC setup/code to suit the cryptic Czech specs (see Notes) seemed a quick route to the required programmer.
Employing KISS, I tinkered a prototype together (as Morbius would say).
Here's the result. And the code. Note that my MK14 is 4MHz (makes timings easy).

The schematic's by hand so a few shortcuts (we all know how NPN looks).
Compare with the SoC ancestor.
Devices:
C - is 74C906
I - inverter. (Me = 4001)
N - 1N4001
O - Si diode. (OA200)
T - Tristate buffer. (74LS125)
- - 6V2 and 12V Zeners.
X - BC237 or similar. (BC184)
Y - 2N3053
Z - NPN to sink min 300mA. (BFY50) TESLA datum is 150mA from programming o/p.

PB5 just switches 5v Vcc, PB6 10v Vccp, and PB7 controls Output Enable.
C1 in Vccp circuit increased to 'slow' the slew.
DLY instructions allow fine tuning of the pulse widths. See annotation for 'zap' timings.
With my (minimally) highest 12V Zener the PROM wouldn't program. Needed Si diode. This raised Vccp at pin16 from
~9V6 to ~9V9 (accurate?) and new contents 'stuck'. (Or one could have used a 13V Zener - if one had had one.)

I've only amended the PROM Editor. I didn't try varying the 1mS program pulse.
I didn't worry about the Vccp duty cycle, even between bits in one location. The code 'fires' all four sequentially, even if '0'.
And the manual interventions to select location/content mean the chip is powered down almost permanently.
1mS program pulse means the recommended duty cycle should be observed if a version of the SoC rapid block-copy 'Promblower' is attempted.

Notes
a) It's the Czech that's cryptic! That programming protocol looked familiar.
Yes. It's almost IDENTICAL (even to the 'X' and 'Y'!) to that given for early (c.1975) Texas Instruments PROMS.
(The duration of TI programming pulse X is not given exactly.)
Can't be coincidence. Extreme Soviet reverse-engineering?
See below, then the TESLA data make more sense:
*
b) If there was a TI SN74S571N I have yet to see the datasheet. And I haven't met any TI 512W x 4B .
Attached Thumbnails
Click image for larger version

Name:	TESLAprogrammer.jpg
Views:	366
Size:	30.5 KB
ID:	191302   Click image for larger version

Name:	part old TI page 2.JPG
Views:	233
Size:	70.5 KB
ID:	191304  
Attached Files
File Type: pdf TESLA Editor.pdf (367.2 KB, 277 views)
File Type: pdf old TI page3.pdf (1.78 MB, 210 views)
circuitryboy is offline