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.

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

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

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

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

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

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.

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

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.

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??

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.

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)??

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

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..!!

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.