Data sheet acquired from Harris Semiconductor. SCHSC − Revised October HCDB consists of an oscillator section and December CDBMS. CMOS 14 Stage Ripple-Carry Binary Counter/ Divider and Oscillator. DATASHEET. Pinout. Functional Diagram. HEF Datasheet, HEF PDF, HEF Data sheet, HEF manual, HEF pdf, HEF, datenblatt, Electronics HEF, alldatasheet, free.

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Another link from an Illinois ECE college course states: It uses a Everything is built on pad board using Road Runner wiring to connect all the components together.

This will increase the stability of your clock. This is negligible for most frequencies, but if you are operating in the RF spectrum this quickly becomes problematic. Solderless breadboards are further limited by their voltage and current ratings. The output datasjeet from IC10A also goes out to the minutes counter, which has to be advanced at every overflow of datasheer seconds counter. When the second decade reaches 6 the output of IC10A will go low.

Maybe this should be another question My way of keeping this site alive. The Minutes Counter Next stop, the minutes counter.

IC4B tries to do the same for the 0. Sign up using Facebook. Due to large stray capacitance from pF per contact pointhigh inductance of some connections and a relatively high and not very reproducible contact resistance, solderless breadboards are limited to operation at relatively low frequencies, usually less than 10 MHz, depending on the nature of the circuit.

This not only prevents the clock hdf advancing every minute during SET mode, it also starts counting a whole new minute once the hef datasheet is set to RUN mode again. It also produces several other division ratios.

Basically, the intrinsic capacitance of the breadboard may already be equivalent to the needed crystal load caps. Let’s start simple, the buttons, which are used to set the time.


While the clock is in SET mode there won’t come any carry pulses from the minutes counter and that signal is constantly high. The 16Mhz one datashedt have some problem, because it starts to oscillate only if I remove the capacitor between PIN11 and ground.


This reset pulse is also used as carry to the hours counter. Sign up or log in Sign up using Google.

At the end it will produce an accurate frequency of 2Hz on output pin 3. Test at lower frequencies and see what happens.

Post Your Answer Discard By clicking “Post Your Answer”, you acknowledge that you have read our updated terms of serviceprivacy policy and cookie policyand that your continued use of the website is subject to these policies. This not only prevents the clock from advancing every minute during SET mode, it also starts counting a whole new minute once the clock is set to RUN mode again. Note from the datasheet that the lower end of the maximum frequency at 12V is about 12 MHz the typical value is much higher, but you can’t really count on it because it is not guaranteedbut this was probably rated with device properly bypassed on a pcb.

There’s one output we might use though.

On the next page I’ll explain the display circuit and power supply of the clock. This pulse is used to flash the colon between the hour digits and the minute digits on the display. Problem is that I have fixed values on the output pins! IC4B tries to do the same for the 0. Hrf4060 would make sure the capactor values C6 and C7 are within the range reccomended in the crystal data sheet. The 14 stage counter is receiving a signal from the oscillator stage as I can see it on the pin 9 but doesn’t count.

The Wikipedia Page on them states pF per contact pointso you may have far datahseet much capacitance on your crystal When the clock is switched to SET mode though, the SET line goes low, which keeps the reset line to the seconds counter constantly high, preventing the seconds counter to count.

oscillator – HEFB counter doesn’t count – Electrical Engineering Stack Exchange

The problem could be related to testing at near the device’s maximum frequency on a breadboard. Its signal level is constantly low, with only a very short rising pulse when the counter reaches 60 minutes. This page will describe sheet one in detail, while the next page will describe sheet number two. Both buttons have a debouncing capacitor in parallel to make sure that every button press results in just one pulse.


BPete This could be a problem with the original 16MHz crystal Unfortunately I don’t have the datasheetbut the 11MHz one that I used, with 22pF capacitors, is the one that I used in dozens of other circuits, without problems. Home Questions Tags Users Unanswered. This counter is also formed by 2 decade counters. In my case the pulse was about ns wide. The Hardware Part 1 You can download the circuit diagram here.

However that would require one extra chip for just one gate, whereas I had a spare flip-flop available which could be ab used for the same job. Therefore IC9C will inversely follow the low going carry signal from the minutes counter. Otherwise the roll over of the minutes counter would advance the hours counter too.

IC4A divides the 1Hz pulse by Once the counters reach that state they are reset back to 0 again. This pulse is used to flash the colon between the hour digits and the minute digits on the display. datawheet


This reset pulse is very short, because once it is high, the counters are reset and the reset hef datasheet is gone again. Insufficient decoupling will cause problems once the circuit starts oscillating, but a complete failure to oscillate is rarely caused by it. The other sheet covers the display circuit and the power supply.

The relative high contact resistance can already be a problem for DC and very low frequency circuits. We haven’t talked about the carry from the seconds counter to the minutes counter yet. The Buttons Let’s start simple, the buttons, which are used to set the time.

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