6502.org

Posted: **Sun Jul 03, 2011 7:26 am**

Quote:

By ordering through mail, is becoming very costly for me a single chip is very expensive + shipping charges....

That's typical anywhere. It's not usually worth it to buy one $2 part and spend $5-$10 or more on shipping; so you just look ahead and get all the parts you might need for this project and others, plus any tools, supplies, etc.. It does take some planning. It's part of being in this field.

Posted: **Sun Jul 03, 2011 7:32 am**

OK, from where to get tell the link, it is Rs 540/.....for me.

Posted: **Sat Jul 16, 2011 4:33 am**

Now 2864 EEPROM is available in my local market, soon i will have it..!!

Posted: **Mon Jul 18, 2011 3:30 am**

GARTHWILSON wrote:

Quote:

I have see that .gif circuit of EEPROM programmer i think here DIP switch are used, we can replace it by 4040 chip 12 bit ring counters

I was thinking the same thing-- to use counter ICs; but 4040's won't let you start at an arbitrary address or back up to correct mistakes. You will want presetable counters like perhaps the 74xx161. It looks like the '191 and '193 also allow counting down as well as up. If you have the counters increment automatically after each programming pulse, you will have to debounce the "program" button. Otherwise you will get a lot of consecutive bytes programmed with the same data where you only pressed the button once.

I would not recommend DIP switches, since they are mostly made for very few cycles of life.

the counter you are telling are 4 bit and 4040 has 12bits counters pls tell any 12 bit up/down counter for EEpROM.....

Posted: **Mon Jul 18, 2011 4:19 am**

4-bit counters will work. You just cascade them, making the "carry" output of one go to the input clock of the next.

Posted: **Mon Jul 18, 2011 5:34 pm**

hi, which chip will be better 74xx161,191 or 193 i found that 161 was used in flash ROM something like this...??

Posted: **Mon Jul 18, 2011 8:46 pm**

I can't take much time right now to compare them in detail, but with a quick look in the data book, it appears that the main differences are that the '161 has a count-enable line whereas the '191 and '193 have an up/down pin instead, and the 193's borrow pin replaces the 191's max/min pin. I suspect the '193 would be best, but it will take more study to confirm. It might be convenient but not necessary to be able to count down as well as up. If it's for a manual programmer, it might be nice to have a decrement-address key. Without it, you would have to be able to enter the starting address again at a lower number and then go forward since you can't go backwards.

Posted: **Tue Jul 19, 2011 5:48 am**

Watch out, IIRC some of them are ripple counters, while others are synchronous.

With ripple counters, for example when the counter switches from $F to $0, the signal "ripples" though the data bits, with noticeable delay. So you can get quite some delay in total and intermediate values. Synchronous timers put their signal out at the same time (which does not mean that there are no intermediate values, but on a much smaller time scale)

André

Posted: **Tue Jul 19, 2011 5:59 am**

The '161, '191, and '193 are all synchronous; but I don't think it would really matter because even if they were ripple, they won't be rippling during the programming pulse.

Posted: **Thu Jul 21, 2011 4:12 pm**

In these counter 191 and 193 i don't understand what is the use of input pins, vice versa??
as we only want 4 bit bidirectional up/down ripple counter...

and what is difference in working of synchronous counters??

Posted: **Thu Jul 21, 2011 8:43 pm**

Quote:

i don't understand what is the use of input pins

to tell it what number you want it to start at, so you don't have to start from zero or some random number

In a ripple counter, there will be a small delay from the changing of the lsb to the changing of the msb. In a synchronous counter, the new outputs will all be reflected simultaneously. I don't think it will matter for a programmer, because what happens between programming pulses will not matter as long as the EEPROM's setup and hold times are met.

Posted: **Fri Jul 22, 2011 3:40 am**

That's good that we can start from any numbers...!!

and one more question the output pins of this counters should be connected directly to EEPROM or with a Transistor (amplifying current)??

Posted: **Fri Jul 22, 2011 4:38 am**

Any of the logic families starting with "74" will provide more than adequate drive, so there's no need to amplify.

Posted: **Wed Jul 27, 2011 2:28 pm**

Hi again,

I have buy both 74193 and 2864 chip please tell how to start the hardware for programmer...

as i will use 74193 for add. and switches for programming..!!

Posted: **Thu Jul 28, 2011 4:26 am**

Quote:

as i will use 74193 for add. and switches for programming..!!

The 74193 is working fine but the problem is some time when switch is pressed once the the counter jump from 1 to 3 like ths.....

I think this the problem of debounce..!!

please help.

6502.org

How to Start hardware of 2864 EEPROM Self made circuit...??