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.

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).

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).

Rumour says that i2c sensor manufacturers like to put a 8051 on the silicon for running its state machine.

Each time the same mask. And a lot of the code is reusable and proven working million of times.

True, the 8051 inside the FX2 is primarily used to assist in the setup of the USB endpoints and such.  But, I used the FX2 chip to do a whole lot more.  I built a DSP-based data collection device, with FX2 chip as the USB transceiver.  I ended up having the FX2 fully involved in booting up the DSP and controlling several board features.  I directed a USB endpoint to the 8051 and decoded packets perform various features/functions.

The FX2 was a steep learning curve, but I really did enjoy using that chip. 

Makes sense.. Sounds perfect for dropping a tiny 8051 in some area of the chip : ) 

It's a great chip, although as you say quite a learning curve. Cypress didn't help matters when FX3 was released, they mixed up a lot of FX2 and FX3 documentation online, and as a result it's really quite hard to set up a development environment for FX2, the links to resources point all over the place : ( Plus then the whole Zadig thing was an irritant, I wish they had EEPROM internally to the FX2 for all that.

I think I eventually managed to have an environment that would build for FX2, but no idea how I got there, I had to install and uninstall quite a few things!

May I ask what chip is that, 8051 code + USB + ADC? Does it have a Jtag that I can use for Assembly debugging? And how do I search microcontrollers with 8051 code + extra features?

Silabs have a range of 8051+ processors. The last one I used was a 100MHz variant. (And thats 2 clock per machine cycle as well !).

https://www.silabs.com/mcu/8-bit-microcontrollers

Some of the peripherals (especially ADC) are pretty good.

But a 50MHz ARM Cortex is now much cheaper and much faster.

I haven't used an 8051 for about 16 years !

MK

during a quick search for 16KB FLASH '51 I have found for example C8051F321-GM (expensive and rather outdated [not recommended for new designs]) but with USB, ADC and a debug interface it seems

Hi,

The one I was looking at is very niche, it wouldn't be useful for general 8051 microcontroller development. However as Michael says, Silabs has general-purpose 8051 chips, with ADC and USB. They will have debugging capability, perhaps with their own debugger and tools.

If it were me, I would look for a very close replacement (since you mention it's a commercial purpose), but not concentrate on using 8051 assembly for new projects because with C programming (for future projects) you're not tied down to a limited range of devices.