Author Topic: 8-bit uC - is there even a point?  (Read 25218 times)

0 Members and 1 Guest are viewing this topic.

Offline nctnico

  • Super Contributor
  • ***
  • Posts: 18266
  • Country: nl
    • NCT Developments
Re: 8-bit uC - is there even a point?
« Reply #200 on: October 01, 2018, 02:55:03 pm »
NXP still makes one with 28 pins!
https://www.nxp.com/part/LPC1114FN28

Thanks nctnico, but what the $&%... can't find/buy it anywhere, must be made of unobtanium! :-)
Newark says they have it available in the near future. Given the component shortages it doesn't surprise me. Try to buy 100nf 0603 capacitors...  :scared:
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline langwadt

  • Super Contributor
  • ***
  • Posts: 1606
  • Country: dk
Re: 8-bit uC - is there even a point?
« Reply #201 on: October 01, 2018, 04:08:18 pm »
NXP still makes one with 28 pins!
https://www.nxp.com/part/LPC1114FN28

Thanks nctnico, but what the $&%... can't find/buy it anywhere, must be made of unobtanium! :-)
Newark says they have it available in the near future. Given the component shortages it doesn't surprise me. Try to buy 100nf 0603 capacitors...  :scared:

digikey has plenty

 

Offline blueskull

  • Supporter
  • ****
  • Posts: 12602
  • Country: cn
  • Power Electronics Guy
Re: 8-bit uC - is there even a point?
« Reply #202 on: October 01, 2018, 04:09:51 pm »
What is the thing with DIP? Are they still being used by any mass produced products?
The only DIP chips I can still think of are DIP4 optocouplers and DIP8 integrated flyback SMPS chips.
For the sake of love, I've not used a DIP for years, literally years, besides student teaching projects.

PS. Also why TSSOP? They are harder to hand solder than DFN/QFN. The gull wing sucks and stores solder, so bridging happens all the time with short pad extension. With QFN, I can do 0.2mm extension per side and they still don't bridge.
 
The following users thanked this post: hans, ogden

Offline coppice

  • Super Contributor
  • ***
  • Posts: 4891
  • Country: gb
Re: 8-bit uC - is there even a point?
« Reply #203 on: October 01, 2018, 04:26:03 pm »
What is the thing with DIP? Are they still being used by any mass produced products?
The only DIP chips I can still think of are DIP4 optocouplers and DIP8 integrated flyback SMPS chips.
For the sake of love, I've not used a DIP for years, literally years, besides student teaching projects.

PS. Also why TSSOP? They are harder to hand solder than DFN/QFN. The gull wing sucks and stores solder, so bridging happens all the time with short pad extension. With QFN, I can do 0.2mm extension per side and they still don't bridge.
If you want to use a single sided SRBP PCB, as many whites goods makers still do, DIPs are the prefered package.
 

Offline Mechatrommer

  • Super Contributor
  • ***
  • Posts: 9320
  • Country: my
  • reassessing directives...
Re: 8-bit uC - is there even a point?
« Reply #204 on: October 01, 2018, 04:59:55 pm »
What is the thing with DIP? Are they still being used by any mass produced products?
The only DIP chips I can still think of are DIP4 optocouplers and DIP8 integrated flyback SMPS chips.
besides SMPS PSU you mentioned that alone can count in millions, DIP are in gazillions in home appliances such as heater shower, water heater, refrigerator, air conditioning, toaster everything but highly densed electronics/computing related stuffs.
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline blueskull

  • Supporter
  • ****
  • Posts: 12602
  • Country: cn
  • Power Electronics Guy
Re: 8-bit uC - is there even a point?
« Reply #205 on: October 01, 2018, 05:47:45 pm »
If you want to use a single sided SRBP PCB, as many whites goods makers still do, DIPs are the prefered package.

Just use an SOP as a DIP. Fan out the pins and it's virtually a DIP, without the high package material cost and manual part insertion cost.
 

Offline nctnico

  • Super Contributor
  • ***
  • Posts: 18266
  • Country: nl
    • NCT Developments
Re: 8-bit uC - is there even a point?
« Reply #206 on: October 01, 2018, 05:50:03 pm »
If you want to use a single sided SRBP PCB, as many whites goods makers still do, DIPs are the prefered package.

Just use an SOP as a DIP. Fan out the pins and it's virtually a DIP, without the high package material cost and manual part insertion cost.
DIPs can be placed automatically for decades.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline wraper

  • Supporter
  • ****
  • Posts: 10575
  • Country: lv
Re: 8-bit uC - is there even a point?
« Reply #207 on: October 01, 2018, 05:54:16 pm »
Modern single layer PCBs usually consist of largish SMT parts glued on the bottom including ICs and through hole parts and jumpers on the top. Like electrolytic capacitors, power semiconductors, optocouplers. All of it is wave soldered, no reflow. If it's simple circuit, it may be through hole only as well.
 

Offline blueskull

  • Supporter
  • ****
  • Posts: 12602
  • Country: cn
  • Power Electronics Guy
Re: 8-bit uC - is there even a point?
« Reply #208 on: October 01, 2018, 05:54:46 pm »
DIPs can be placed automatically for decades.

Don't think that's true for China, or maybe I'm wrong.
In my mind, automatic THT placement is expensive and prone to failure, way more expensive than SMT.
 

Offline wraper

  • Supporter
  • ****
  • Posts: 10575
  • Country: lv
Re: 8-bit uC - is there even a point?
« Reply #209 on: October 01, 2018, 05:58:05 pm »
DIPs can be placed automatically for decades.

Don't think that's true for China, or maybe I'm wrong.
In my mind, automatic THT placement is expensive and prone to failure, way more expensive than SMT.
Automated through hole placement is slow and easy to screw up. I don't think it 100% of parts are automated even at places with machine placement.
 

Offline wraper

  • Supporter
  • ****
  • Posts: 10575
  • Country: lv
Re: 8-bit uC - is there even a point?
« Reply #210 on: October 01, 2018, 06:00:35 pm »
Like here at 4:30, they machine place TH capacitors but other stuff is placed by hand.

https://youtu.be/ylk6VMBLrvM
 

Offline langwadt

  • Super Contributor
  • ***
  • Posts: 1606
  • Country: dk
Re: 8-bit uC - is there even a point?
« Reply #211 on: October 01, 2018, 06:02:30 pm »
Modern single layer PCBs usually consist of largish SMT parts glued on the bottom including ICs and through hole parts and jumpers on the top. Like electrolytic capacitors, power semiconductors, optocouplers. All of it is wave soldered, no reflow. If it's simple circuit, it may be through hole only as well.

if it has bunch of big connectors you might have to do wave solder any way so going all through hole might same a few steps
 

Offline wraper

  • Supporter
  • ****
  • Posts: 10575
  • Country: lv
Re: 8-bit uC - is there even a point?
« Reply #212 on: October 01, 2018, 06:06:09 pm »
Modern single layer PCBs usually consist of largish SMT parts glued on the bottom including ICs and through hole parts and jumpers on the top. Like electrolytic capacitors, power semiconductors, optocouplers. All of it is wave soldered, no reflow. If it's simple circuit, it may be through hole only as well.

if it has bunch of big connectors you might have to do wave solder any way so going all through hole might same a few steps
Nobody does reflow soldering on single layer phenolic PCBs to begin with. There is additional assembly step but PCB goes through soldering only one time.
 

Offline nctnico

  • Super Contributor
  • ***
  • Posts: 18266
  • Country: nl
    • NCT Developments
Re: 8-bit uC - is there even a point?
« Reply #213 on: October 01, 2018, 06:09:00 pm »
DIPs can be placed automatically for decades.

Don't think that's true for China, or maybe I'm wrong.
In my mind, automatic THT placement is expensive and prone to failure, way more expensive than SMT.
Automated through hole placement is slow and easy to screw up. I don't think it 100% of parts are automated even at places with machine placement.
I visited a TV manufacturing plant from Nokia in Germany in the early 90's and even back then they placed all through-hole components automatically. The machines would even detect a failure, pull the part back out (bin it) and re-insert a new one. I'd say those through hole placement machines where more impressive than those newfangled SMT p&p machines  8)
The SMT parts where glued to the solder side and the whole PCB would then go through the wave soldering machine.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline blueskull

  • Supporter
  • ****
  • Posts: 12602
  • Country: cn
  • Power Electronics Guy
Re: 8-bit uC - is there even a point?
« Reply #214 on: October 01, 2018, 06:20:10 pm »
I visited a TV manufacturing plant from Nokia in Germany in the early 90's and even back then they placed all through-hole components automatically.

A company can utilize such a machine will definitely grow out of THT in 2018. A company that still is stuck with THT can't justify such a machine.

FYI, a product line worker in Shenzhen works 12 hours a day, 6 days a week, can stuff a part in less than 5 seconds, and gets paid $500 per month. That's around 500 parts per dollar.

A modern machine can beat that price, but only at very high volume.
 

Offline wraper

  • Supporter
  • ****
  • Posts: 10575
  • Country: lv
Re: 8-bit uC - is there even a point?
« Reply #215 on: October 01, 2018, 06:23:05 pm »
I visited a TV manufacturing plant from Nokia in Germany in the early 90's and even back then they placed all through-hole components automatically. The machines would even detect a failure, pull the part back out (bin it) and re-insert a new one. I'd say those through hole placement machines where more impressive than those newfangled SMT p&p machines  8)
The SMT parts where glued to the solder side and the whole PCB would then go through the wave soldering machine.
That's probably one of the reasons why Nokia TVs are not made since 1996.
 

Offline coppice

  • Super Contributor
  • ***
  • Posts: 4891
  • Country: gb
Re: 8-bit uC - is there even a point?
« Reply #216 on: October 01, 2018, 07:12:38 pm »
DIPs can be placed automatically for decades.

Don't think that's true for China, or maybe I'm wrong.
In my mind, automatic THT placement is expensive and prone to failure, way more expensive than SMT.
There are many automated THT lines in China.

THT placement has been cheap and highly reliable since DIP devices first appeared. That is why the design of the DIP package has the legs splayed. That was specifically so the machines could flex them in and they would spring back enough to secure the device until it reached the wave soldering station. Its why resistors and capacitors come on taped reels. The placement machines clip them out of the reel, form the legs, and stuff them into the board. In most cases the legs are left long. After the wave soldering step a really brutal looking machine slashes off the excess length of all these overly long legs in one operation.

For many years THT placement was much more reliable than SMT placement, as SMT placement is prone to things getting shaken out of place. The industry went through several generations of glue spot/don't glue spot/glue spot and other techniques before settling down to modern practices.This kind of thing is rarely a problem with automated THT lines.
 

Online westfw

  • Super Contributor
  • ***
  • Posts: 3098
  • Country: us
Re: 8-bit uC - is there even a point?
« Reply #217 on: October 01, 2018, 07:39:30 pm »
Quote
Absolutely smallest and cheapest won't have core-coupled RAMs, of course.
If you meant the "Tightly Coupled Memory" (TCM) feature provided by ARM, that's an OPTION in CM7, not available at all in CM0 through CM4.  (According to the wikipedia table.  OTOH, the SAMD51 claims to have TCM, and the WP table also claims that M0, M3, M4 don't have cache, either.  While several data sheets claim to have simple caches.  (I assume that this is the difference between implementing the cache in the vendor-provided memory system vs using the ARM-provided IP.  In which case I don't know what Atmel/Microchip means by "TCM"...)
So, a very small number of ARM chips have TCM.Many ARM have RAM that is faster than their flash, and you can put code there if you want faster execution.  But we were talking more about determinism than raw speed, I thought.  (and "just put your critical code in executable RAM" is right up there with "just use bank select of you need more than 64k of data" - possible, but a bit contradictory with the the "simple" claims.)

 

Online ogden

  • Super Contributor
  • ***
  • Posts: 2804
  • Country: lv
Re: 8-bit uC - is there even a point?
« Reply #218 on: October 02, 2018, 12:57:26 am »
Quote
Absolutely smallest and cheapest won't have core-coupled RAMs, of course.
If you meant the "Tightly Coupled Memory" (TCM) feature provided by ARM, that's an OPTION in CM7, not available at all in CM0 through CM4.

Indeed he did mean Core Coupled Memory (CCM). CCM is additional small RAM segment with own bus interface. STM32 F3 series have 8KB CCM RAM. Don't know about other manufacturers/chips. Actually useful for busy MCU's - CPU can fetch instruction or do whatever it pleases with CCM RAM while (during same clock cycle) DMA is doing transfers using main RAM.

More info about stm32 CCM here
« Last Edit: October 02, 2018, 11:53:10 am by ogden »
 

Offline richardman

  • Frequent Contributor
  • **
  • Posts: 427
  • Country: us
Re: 8-bit uC - is there even a point?
« Reply #219 on: October 02, 2018, 01:53:09 am »
Well, this post certainly wanders all over the place ;-)
// richard http://imagecraft.com/
JumpStart C++ for Cortex (compiler/IDE/debugger): the fastest easiest way to get productive on Cortex-M.
Smart.IO: phone App for embedded systems with no app or wireless coding
 

Online KL27x

  • Super Contributor
  • ***
  • Posts: 3734
  • Country: us
Re: 8-bit uC - is there even a point?
« Reply #220 on: October 02, 2018, 05:03:29 am »
Quote
What is the thing with DIP? .... For the sake of love, I've not used a DIP for years, literally years, besides student teaching projects.
I bet by the time you used your first SMD chip, other people had been using them for years, literally years.

The reason, as far as the manufacturers are concerned, is because of branding/marketing/education. If some n00b chooses TI over Maxim IC because it comes in DIP, he might end up buying hundreds of thousands of (SMD) TI parts in the future, just because that's what he is familiar with. 

Quote
PS. Also why TSSOP? They are harder to hand solder than DFN/QFN. The gull wing sucks and stores solder, so bridging happens all the time with short pad extension. With QFN, I can do 0.2mm extension per side and they still don't bridge.
At least one practical reason is that QFN are more culpable to cracked solder joints due to board flex and/or thermal expansion/cycling. The difference has been tested. And regarding deep thermal cycling, apparently gull wing chips can be more than an order of magnitude better in some of these tests.
« Last Edit: October 02, 2018, 05:05:02 am by KL27x »
 
The following users thanked this post: petert

Online ogden

  • Super Contributor
  • ***
  • Posts: 2804
  • Country: lv
Re: 8-bit uC - is there even a point?
« Reply #221 on: October 02, 2018, 08:35:33 am »
Well, this post certainly wanders all over the place ;-)

If you think something is wrong in that particular post - then provide correct information.

[edit] If you have problems using internet search engines to check keywords I did provide, you are welcome to read this document.
« Last Edit: October 02, 2018, 11:58:16 am by ogden »
 

Offline Siwastaja

  • Super Contributor
  • ***
  • Posts: 2120
  • Country: fi
Re: 8-bit uC - is there even a point?
« Reply #222 on: October 02, 2018, 09:11:13 am »
Quote
Absolutely smallest and cheapest won't have core-coupled RAMs, of course.
If you meant the "Tightly Coupled Memory" (TCM) feature provided by ARM, that's an OPTION in CM7, not available at all in CM0 through CM4.

I don't know what any table says, and I'm not always exactly correct. But, I have been happily using fast core-coupled RAMs for timing critical and deterministic interrupt stuff in MCUs with CM3 and CM4 cores, and being non-existing or imaginary, I have measured them working remarkably well!

STM32F334 being one such example I can remember*. Clearly, it's ST's addition, and not the "ARM's option". The name is "CCM" for core-coupled memory instead of "TCM". This terminology is similarly irrelevant as is the classical discussion on "who's fault the bug is". I buy real MCU's based on what they offer and how they perform. An actual $3 ARM MCU offering me way better performance than a $3 8-bitter (including real-world interrupt latency, measured on real-world terms; I use oscillosscope to measure from trigger to result) and way better peripherals offloading the CPU even further, is the fact of reality, and as I have stated earlier, it has quite little to do with ARM exactly. IMHO, ARM core is boring enough not to be fanboy'ed over.

*) I did something similar on STM32F205 on its another extra SRAM, but it shares the bus and hence, heavy DMA traffic can cause a few clock cycles of jitter on interrupt latency during stack push, which is guaranteed 50% of bus arbitration cycles. Whether this is important, when the actual interrupt processing latency at 120MHz is still likely to be faster than on almost any 8-bitter, is up to you decide.

But yeah, I have also put a single quickly-needed instruction on the AVR's interrupt table directly, avoiding the delay of the jump. At 20MHz, this is very fast as well, and indeed will outperform a cheap M0 stacking registers through a bus also used by DMA. But most of the time, the timing-critical interrupts are longer than that, and the important result happens later than at the first machine instruction.

I mostly use the very cheapest 8-bitters only, but I guess most share this viewpoint nowadays; the "large $5 AVRs" make even less sense today than they made a decade ago.
« Last Edit: October 02, 2018, 12:22:27 pm by Siwastaja »
 
The following users thanked this post: ogden

Offline Mr. Scram

  • Super Contributor
  • ***
  • Posts: 8192
  • Country: 00
  • Display aficionado
Re: 8-bit uC - is there even a point?
« Reply #223 on: October 02, 2018, 10:20:14 am »
I bet by the time you used your first SMD chip, other people had been using them for years, literally years.

The reason, as far as the manufacturers are concerned, is because of branding/marketing/education. If some n00b chooses TI over Maxim IC because it comes in DIP, he might end up buying hundreds of thousands of (SMD) TI parts in the future, just because that's what he is familiar with. 

At least one practical reason is that QFN are more culpable to cracked solder joints due to board flex and/or thermal expansion/cycling. The difference has been tested. And regarding deep thermal cycling, apparently gull wing chips can be more than an order of magnitude better in some of these tests.
I understood that QFN is actually one of the most reliable packages from a mechanical point of view. I think I read about this in a paper somewhere, but I don't think I'd be able to find that again. I stand to be corrected.
 

Offline Rerouter

  • Super Contributor
  • ***
  • Posts: 4430
  • Country: au
  • Question Everything... Except This Statement
Re: 8-bit uC - is there even a point?
« Reply #224 on: October 02, 2018, 12:15:58 pm »
QFN is reliable, so long as you have soldermask spacing, e.g. not pad flat to copper with no gap for the solder, this gives it some distance to keep forces inside the elastic zone of deformation. similar to BGA, if you didn't have the balls at the right height they just rip pads off either the chip of the board when flexed,

Though I still see the center pad of QFN's a right pain to get right every time, you have to generally get weird with your paste masks to get better than 99.9% yields, which generally leads me to fitting a dot when its needed, vs a full pad,
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf