4-bit MCU Availability - Again

This one at least have an email you can try:

snipped-for-privacy@tritan.com.tw

No way to look at datasheets. They require you to login, but no way to register to get a login. So no idea what their products are like. I'm not interested enough to email them if I can't even view a data sheet. Insane!

I recall companies (mostly Asian) who provide data sheets, where copying text is locked out! Why would anyone want to prevent me from copying details of their data sheet? It makes it very inconvenient for me to include their data in my board documentation and does NOTHING to prevent their competition from gaining access to it.

The world is weird.

Thanks for the link. At least I know of two companies who make these things. What I'd really like to know is how many they sell each year. I'm thinking it's a LOT since so many products use them. Some have suggested many of those products are using 8 bit MCUs. There's one Chinese company that is available on LCSC with an 8-bit MCU at about $0.03 each, qty 100. That's insane!

In addition to the cost, there's the power issue. Remote controls need to be as low power as possible.

istm that power isn't _that_ critical in a remote control, it only needs to run when you push a button and then the major power consumption is the transmitter

"Isn't *that* critical"? No, nothing about a remote control is *critical*. The lower the power, the better until you match the self current of the battery. Given the battery lasts as long as 10 years on the shelf, I've never had a remote battery last that long. Also, the lower the current drain, the smaller the battery can be. They tend to be AAA now.

The MCU has to run all the time to "see" that you pressed a button. It doesn't have to run 100% of the time to do that, but it's a far cry from only when you press the button. It's not like the MCU is just turned off and you press a button to turn on the remote, then press the button you want to send. I suppose they could diode OR the buttons to the MCU power connection, so the MCU is off until a button is pressed. Do they do that? I guess they want to save the cost of the diodes, so instead they use a 4-bit MCU that draws very, very little current when running.

MCU draws very little current when sleeping, then wake up on button interrupt.

Were you able to download information on these ? The product table has a download column on the right side but they appear to be dead, even looking at the source there is nothing.

boB

No, I got nowhere. Tritan was no better requiring a login while not allowing you to sign up

That is far from clear. Once you go below 1uA standing current the battery life might even be slightly enhanced by a tiny current flow.

Most of them can be configured to be at least an order of magnitude less around 0.1uA in sleep mode and have a wake up on button pressed.

10uA standby will last 10 years on 1000mAh battery. If the OP is willing to spend a few more cents, an 8 bit OTP MCU is far more capable (including A2D):

What makes you think you can't get an ADC in a 4-bit MCU?

You never understand the design process. At qty 1,000,000, no one cares about having "more capable" processors. They need what they need and will pay for nothing extra. I guess this doesn't surprise me, coming from you.

On many remote controls, there are enough buttons they need to be multiplexed. I suppose it is possible to connect every I/O pin to a change detector.

"Fancier chips" is not what this is about. It is about the absolute lowest cost product. Even the pin state change detector might price the device above the competition. Not only is there die area costs, but tiny chips like these are dominated by the time spent on the tester.

This is the sort of situation where you can devise all sorts of fancy fasteners that have many advantages, but a nail is going to win the contest every time.

Keeping the entire chip in zero power state other than a low rate RC oscillator to wake up the device is going to win this contest every time. For the remote control, it has to wake up maybe 5 times a second to prevent perceptible lag. The CPU probable runs at a similarly slow clock rate, then shuts off. This is going on 24/7, so needs to be adequately low.

You can still multiplex on pin change interrupt. The Holtek chip has 18 to 26 pins to multiplex.

So, not much difference between 4 bits or 8 bits. You are dealing with much smaller segment in 4 bit manufacturers, and they usually want more profit.

The Holtek chip can run on timer interrupt at 10uA for 10 years. Spec-ing battery for more than 10 years is just meaningless.

I have done pin change interrupt on 32KHz AVR. There was no perceptible lag. It takes more time to turn on the LCD than interrupt trigging.

Humans are pretty slow when compared to a 32kHz clock. The chips I use actually clock at 8kHz when used with a 32kHz watch xtal. You still can't notice any lag on button press.

Once you are running on a low power watch crystal and in a decent low power mode it doesn't make much difference to battery life whether the thing draws 1uA or 0.1uA. Even as much as 10uA still gives you 10^5 hours or >10 years per Ah of battery.

There is a tendency to use micro button cells with lower capacities in tiny remotes these days but even so the 24/7 CPU drain is miniscule when compared to the transmit power of the IR or RF when sending a command.

We did a project with the $1 AVR and 25c Holtek equivalent OTP chip. AVR draws more power when running, but less in sleeping. Our customer did not ask for cheaper chip (in 10k Qty) or longer battery life.

I don't know all your requirements so pls take these suggestions as just that. You may have already checked them out. J

I don't see much power-saving advantage to a 4 bit CPU, either, modern 8 bit microcontrollers can be put into sub-uA sleep waiting on a pin change interrupt.

Can they be put to sleep waiting for any key on the keypad to be pressed? I've just never seen a device that had that flexibility.

I was actually hoping to hear from some people who design products that sell millions and only have a need for a very limited processor, like a 4 bit device. There was one guy in particular who used to post here and designed toys. He talked about design reviews removing a resistor they felt was not important enough to retain because of the cost.

Yes, that's the point of pin change interrupt. As long as you have the trigger pins (if not all) on the rows or columns of a matrix, it will wake up on any key. This is a very common feature on almost all micros: msp430, avr, pic, etc.

As you said before, the price difference between 4 bits and 8 bits will be overwhelmed by setup, programming, testing and packaging costs. Unless you are ready to commit to 1M OTP parts now, you have to worry about them still available when you are ready for volume. When customer says they will buy hundreds of thousand, we usually go with 10k batch to start.