People Still Trying to Use Old Chips?

(instructions, reset, WDT, specifications...) PIC12F6xx, PIC16Fxxx, PIC16F6x, PIC16F7x

People Still Trying to Use Old Chips?

Postby Tom Maier » Mon May 26, 2014 3:33 pm

Notice how some people (new to pics) are still trying to use the ancient chips like 16F84? I think this is caused by having so much ancient material out there and the new people fall into microchip that way. Then it becomes hard to get them to change to something newer. They see old projects on the web and want to start with that, and then get the idea that the microchip parts are still ancient. :D
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Re: People Still Trying to Use Old Chips?

Postby jtemples » Mon May 26, 2014 5:54 pm

At least some of those seem to be forced into using dinosaurs by school labs that haven't updated their equipment in 10 years or more.
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Re: People Still Trying to Use Old Chips?

Postby Tom Maier » Mon May 26, 2014 6:12 pm

I brought that up because there was a guy posting on the microchip forum at a school lab trying to figure out how to use one, probably the same post you are refering to. I imagine the lab was designed 15 years ago and never upgraded.

But aside from that, I see a lot of posts on other firums asking "how do I use a pic16f84?" and the reply I'd like to give is "Please don't."

I built a whole line of products in the mid 1990's around the pic16C54. It was very challenging to use such small space and limited resources. I would hate to see people doing that now days.

And another thing is that some people will just doodle with the 16f84 and then walk away thinking that is the whole microchip product line. I was talking to an engineer and he had "evaluated" the microchip controllers and he said they were too primitive for his application, but when I asked him to describe what he had looked at, he described the '84. Not a good evaluation.
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Re: People Still Trying to Use Old Chips?

Postby Ian.M » Sat May 31, 2014 3:46 pm

Perhaps we need to write some migration guides. Sticking with drop-in replacements for a PIC16x83/84, the cheapest 18 pin standard midrange part is the PIC16F716, and the cheapest with integrated debug support is the PIC16F87.
Points to cover:
* Use of standard headers rather than defining SFRs in one's own code
* Differences in the address map - variables start at 0x20
* Banking and paging differences - apart from the shared memory above 0xF0, the RAM is no longer common to all banks + PCLATH has more active bits.
* Electrical/Functional differences - RA4 is no longer open drain high voltage tolerant. Reduced Abs.Max Vdd limit.
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Re: People Still Trying to Use Old Chips?

Postby ric » Sun Jun 01, 2014 10:45 am

And the 16F877 was the general purpose 40 pin chip of the era, which many people seem to be still asking about.
I've had a few rants on the mchip board about how much better the 16F1xxx equivalents are :)
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Re: People Still Trying to Use Old Chips?

Postby Tom Maier » Sun Jun 01, 2014 1:57 pm

I thought the general purpose micro of the era was 8051. :D

Also, the 'hc11 was pretty popular.

People have been predicting the death of the 8051 line for 25 years now, and it still seems to be alive out there. I don't consider it anymore, because the microchip runs rings around it for features and price. Butt.. it lives on.

When I was teaching I would use 8051 for teaching assembly language and then introduce other processors to make them aware of what else is out there. I liked the 8051 for teaching assembly because it is a lot more straight forward in architecture and has a friendly instruction set. Also, it was easy for them to build a breadboard circuit with micro and uveprom and see it run. Then they could snoop the bus and watch the code being fetched. Having the external code memory gave good opportunity for learnng scope skills and re-enforced the basic concepts of how a micro works.
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Re: People Still Trying to Use Old Chips?

Postby Ian.M » Sun Jun 01, 2014 2:01 pm

The 40/44 pin members of the PIC16F87x(A) family offer a PSP (Parallel Slave Port). That means they can latch 8 bits of data IN HARDWARE when an external strobe is applied and have /CS /RD and /WR inputs allowing them to act as a peripheral on a shared 8 bit parallel bus with access times as low as 120ns. The only other PIC16 chips that offer this are even more antique.

If you are doing something like emulating a HD44780 compatible LCD, and want a midrange PIC then a PIC16F877A may still be an appropriate choice as it will need far less glue logic to present a compatible bus. Of course it would probably make more sense to ignore the midrange devices, save money and use a PIC18F4420.

If the sourcecode is available and the PSP isn't being used then using a PIC16F87x(A) is just dumb unless you need a PIC16 today and that's all the local suppliers stock.
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Re: People Still Trying to Use Old Chips?

Postby SeanD » Mon Jun 02, 2014 6:15 pm

Too true Ian. My personal choices are the 12F1840 and the 16F1847.
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Re: People Still Trying to Use Old Chips?

Postby linker3000 » Tue Jun 03, 2014 6:44 am

Guys,

You have hit the nail on the head - I am just trying to get into PIC programming, and seeking out project examples on the 'net turns up heaps of stuff from way back that uses older chips. I don't know how much work would be involved, but it would be great to see a guide or series of guides along the lines of 'If you see a project using X device, consider using Y instead, but you will need to check out the following differences'. I appreciate that Microchip's data sheets often hint at newer devices, and often have some tips for migration, but finding or working out the info is not always easy - and it's always simpler/lazier if it's all laid out in one place.
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Re: People Still Trying to Use Old Chips?

Postby ric » Fri Jun 13, 2014 12:07 am

As I mentioned, the 16F87x series are still showing up a lot. What would you regard as the ideal enhanced replacement for them?
16F873/6 -> ?
17F874/7 -> ?

e.g. for a PIC16F877 replacement, I tried entering the following minimum requirements into MAPS.
Pins 40, FLASH 14kB, RAM 368, EEP 256, ADC 8, USART 1, SPI 1, I2C 1, PWM 2
and it came back with PIC16F1787 or PIC16F1789

Code: Select all
Chip            PIC16F877   PIC16F887   PIC16F1789
==================================================
Price (PDIP)    $4.94       $2.20       $2.51
Pins            40          40          40
I/O pins        33          35          36
Int clk         No          Yes         Yes
Max clock       20MHz       20MHz       32MHz
FLASH           8kW         8kW         16kW
RAM             368         368         2048
EEP             256         256         256
ADC             8x 10-bit   14x 10-bit  14x 12-bit
FVR             No          0.6V only   Yes
Comparators     0           2           4
Opamps          0           0           3
DAC (5-bit)     0           0           3
DAC (8-bit)     0           0           1
CCP             2           2           3
MSSP            1           1           1
(E)USART        1           1           1E
FSR registers   1           1           2
Linear access   No          No          Yes
HW breakpoints  1           1           3
LAT registers   No          No          Yes
Context saving  No          No          Yes
Stack           8           8           16
R/W stack ptr   No          No          Yes
ADDWFC instr    No          No          Yes
MOVLB/MOVLP     No          No          Yes
MOVIW/MOVWI     No          No          Yes
==================================================
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