Selecting 83C154 (8051) replacement

https://ru.elcodis.com/parts/6051076/83C154_p5.html

the pinout seems to be identical with 8051 - the question is which of 83c154 differences/improvements are in use?

And why 83? Was it using internal, factory-programmed ROM or external program memory was used? What is the size of the code?

If it is using external EPROM, the question is why no other 8x52 can be used? Is very high clock speed needed?

The list of differences seems rather short - according to this https://www.keil.com/dd/docs/datashts/atmel/c51_ao.pdf

difference between 8xc52 and 8xc154 amounts to:

• timers include watchdog and 32bit timer/counter
• serial reception error detection
• new modes for power reduction
• programmable impedance port
• asynchronous counter/serial port mode during power-down
• 16KB of internal ROM

AT89S52 from Microchip is advertised to be in production and a successor of 89C52 (clocked up to 33MHz)

89S52 in DIP40 at Farnell portal

Silicon labs offer 8-bit microcontrollers based off the 8051.

www.silabs.com/.../8-bit-microcontrollers

they realesed new 8051 families in 2021 . It is interesting to see hidden market demands. But of course, they are not compatible with the chip mentioned in question.

Hi,

If it's a project worth doing, it may well be worth redoing in C, replacing with a completely different chip of your preference. Especially if you have the assembler listing and if it's understandable (some are not that easy, but worth closely examining in case it all makes sense).

It could even be mounted on a small board that could be plugged in to the existing microcontroller socket perhaps, if you're using the original PCBs for the project.

I built a DIY project from an article, that uses an 8051-based chip (8051 core in my case), and it's been a constant irritation because I do not have the development environment set up to easily make modifications to suit my needs over the years. If you intend to share your project with others, they too would appreciate a more modern microcontroller and C code rather than assembler, most likely.

If you're talking about a commercial project, then that's a different matter, you may wish to make as few changes to the code as possible to reduce chance of introducing problems, so then I can understand the need to find a close replacement chip. In one project, I had to do something similar (it wasn't 8051), and the replacement happened to be in a different package, so as well as the code changes, there would need to be hardware changes. Rather than change the PCB, an add-on board was created that could be soldered in place.

AT89S52 was my choice of 8051 back in 2013 when I first learning MCU

and it is still actively manufactured I think - it is marked as preferred replacement for 89C52.

I think I have read somewhere that it is connected with intellectual property laws - 8051 arch is so old that it can by freely implemented by anyone

It is possible, but there must be other reasons also. It is questionable if it worth using so old instruction set with many limitations (like crazy limited 8-bit address-space with tons of banking for exposing more memory/peripherals) instead of making new own proprietary new instruction set without these limitations. Silicon Labs show that this instruction set is so popular, that even in 2021, it worth going this way.

I have hear (at university) different reason for 8051 popularity: features to logic gate on die count ratio. 8051 can be implemented with very low count of gates and lower gate count offers smaller dies, decreases probability of manufacturing fault, and so on. While it can be implemented using low count of gates it still offers features for writing almost any program (but still not sufficient for implementing gcc backend).

It also gets used a lot inside chips for 'glue code', e.g. where that microcontroller core is not a key part of the chip, but performs basic housekeeping stuff like initializing things or adding a tiny bit of GPIO etc. In that case, no-one cares about the code running on it, there may be a ROM with it, or RAM for uploading ready-built firmware for that one purpose. 

I'm looking at a chip right now (it's a ADC chip with USB) with a 8051 core, but it doesn't need programming by the end product manufacturer (although they certainly could apply code into RAM if they wished, if they could find the memory+register details. 

Similarly Cypress have a very popular FX2 chip which does USB attachment for hardware, but the 8051 core inside it is only used for some setup stuff, although one can do a lot more with it.

It might be one of the most popular microcontroller cores, since it creeps into so many chips. But (I'm guessing) it's not really the first choice for a standalone microcontroller any more maybe, except to keep old product lines still going (mature products, and those that might need a few tweaks for new customers).