"8749 replaces 8049" Curiosity

[Harbars]

I got rid of the paper sticker that was on - doesn't look like it has any programmability to me, but according to the data sheet this guy includes "2K x 8 UV erasable EPROM". not sure exactly how the UV is supposed to get in!

At any rate, not a Hermes, which I'm slightly annoyed about after being all excited. Where does one find those these days?

[tofro]

This actually is a NEC8749H - which contains an EPROM, the OTP (one time programmable) version. Didn't know this existed.

[mk79]

Ah, shows you learn something new every day. The 8749HC is user programmable, but only once, for low volume prototype runs. I have the 8749HD with the quartz window, which are programmable multiple times.

Hmm, creating Hermes chips is relatively easy if you have the programmer, did one just yesterday to test a bunch of 8749s I got. But I don't really want to get into that shipping business... maybe Rich can be persuaded to sell a new run?

[mk79]

Didn't know this existed.

Same

[Derek_Stewart]

Ah, shows you learn something new every day. The 8749HC is user programmable, but only once, for low volume prototype runs. I have the 8749HD with the quartz window, which are programmable multiple times.

Hmm, creating Hermes chips is relatively easy if you have the programmer, did one just yesterday to test a bunch of 8749s I got. But I don't really want to get into that shipping business... maybe Rich can be persuaded to sell a new run?

Hi,

I bought a batch 10 x NEC D8749HD chips, which all erased Blank check OK, but only 2 programmed the Hermes v2.2 code.

I got a refund on the 8 non-programmable chips and 2 are working in QLs now...

I am just checking if my programmer is working correctly, but it seems to be programming everything else.

[Pr0f]

Ah, shows you learn something new every day. The 8749HC is user programmable, but only once, for low volume prototype runs. I have the 8749HD with the quartz window, which are programmable multiple times.

Hmm, creating Hermes chips is relatively easy if you have the programmer, did one just yesterday to test a bunch of 8749s I got. But I don't really want to get into that shipping business... maybe Rich can be persuaded to sell a new run?

Hi,

I bought a batch 10 x NEC D8749HD chips, which all erased Blank check OK, but only 2 programmed the Hermes v2.2 code.

I got a refund on the 8 non-programmable chips and 2 are working in QLs now...

I am just checking if my programmer is working correctly, but it seems to be programming everything else.

In that DIY Arduino programmer - the inventor there suggested there may be some timing issues for certain signals that can affect the programming - reading was ok, but program / verify could fail - I did wonder if the HiLO units were meeting all the timing specs - they certain do meet the voltages outlined in the 8749 programmers guide - it seemed to vary by chip manufacturer too.

[Derek_Stewart]

Hi,

A couple of thoughts on this.

I will look to see if my Hilo Systems ALL03a programmer is working correctly, all eproms seem to programme okay, when UV erased. Only problems I havw is wi the Intel and NEC 8749.

I note there is a DIY Progammer:

http://www.mattmillman.com/projects/hve ... er-reader/

Which,looks easy to build, I will get some PCBs made.

I also wonder if an replacement 8049/8749 could be made from an Arduino with CapsLockLED builtin to the code.

[Pr0f]

That's the one Derek - see what he says here:

All home-brew MCS-48 programmers have pin drivers resembling the above, mine differs in that it uses a P-Ch FET to get the fastest possible rise time, and a 2K2 “pull-down” is also present to keep fall times within specification (< 2μS).

This is particularly important when programming CMOS parts, otherwise the timings specified in Intel datasheets cannot be achieved, instead arbitrary delays would have to be inserted throughout the programming algorithm to allow charge to bleed away from these inputs, as is frequently seen in other efforts.

The most important difference however, is the 220Ω resistor. Some batches (particularly 8742’s and some 8749’s) are very sensitive to over-current on the PROG pin. I purchased about 50 MCS-48 samples when designing my programmer, and blew a quarter of them discovering this.

This value was chosen because it reliably programs the earliest 1K NMOS parts, which require more current on this pin, and don’t appear to have this problem, while not destroying sensitive 2K parts.

[mk79]

In that DIY Arduino programmer - the inventor there suggested there may be some timing issues for certain signals that can affect the programming - reading was ok, but program / verify could fail - I did wonder if the HiLO units were meeting all the timing specs - they certain do meet the voltages outlined in the 8749 programmers guide - it seemed to vary by chip manufacturer too.

Never had a single chip fail me in the Arduino programmer, yes.

[Derek_Stewart]

Hi,

The 8749 chips that I stated were faulty,I was issued a refund and allowed to keep the chips, so maybe my ALL03a programmer is not up to the job.

Here is another link of someone who has built an the Arduino MCS-48 Shield:
http://www.bygonebytes.co.uk/8748_Programmer.html

I will have to get an Arduino Mega and get short shield PCBs made.