Between 8085, 8051, AVR, PIC and Motorola

[MrZappy]

Hi all, I am a 1st year University Student pursuing a degree in electronics engineering. I am very interested to learn about embedded systems as it is in my syllabus however I find myself being stuck and confused. I hope I can learn most of it before the next semester starts.

1. The main question I have is the difference between 8051, AVR, PIC and Motorola's 68HC11. What is AVR by the way? I know it is manufactured by Atmel but that's all I know. Only the 8051 and 8085 is within my syllabus. Therefore I am more interested to learn up these two types.

2. Is it possible to purchase the necessary components to assemble your own 8051 board at home? I plan to invest a little cash to play with the board at home. Do they come in DIP? Because SMD insn't an option as I don't have the necessary skills to solder it on.

3. Can the 8051 drive motors like the PIC and AVR? Basically, can it do what the other chips can do? What about 8085 then?

4. The language to learn. I understand some language are chip specific. So, how do I go about learning them. I read through the sticky at the start of this forum regarding 8051. It mentions learning up C and using Proteus for simulation. Is this the standard way?

5. Is there any noticeable difference between Intel's 8051 and Atmel's 8051? I understand the technology came from Intel first but what I want to know is whether they are interchangeable. Because I think Intel's 8051 only comes in SMD form whereas Atmel's 8051 comes in DIP. I want to get something that I can experiment at home.

6. I am also interested in robot building. Can I provide the brains of the robot in the form of 8051 or 8085? Because those are the major stuffs that I learn about, I would prefer to use as opposed to PIC. Besides, I heard the 8085 has much more memory capacity as it uses external RAM. Is this true? And can I drive motors with 8051 and 8085? More importantly, can I build the 8085 in the first place?

7. I am thinking of purchasing an Arduino or an Axon but I would prefer if I can make them on my own rather than buy them cause delivery would be a problem. Anyway, what's the difference between them? Is the Axon powerful enough to support a robot in a competition?

Thank you for taking the time to read through my post.

[SmAsH]

Hi there,

1. Well, they are all microcontrollers as you can see. They all have their ups and downs but i would recommend either avr or pic though if you need to use another type, that's fine.

2. Definitely, the 8051 does come in dip and you could get the rest of the components needed for the project easily.

3. Yep, it can drive motors but not directly from the pin, you will need a motor controller/driver, google it

4. Hm, for your microcontroller choice you would probably want to learn C or something close to it.

5. There probably is some difference, i can't say for sure though.

6. Yep, it could be the brains of a robot, Don't know about the external ram though, probably wont need it if you're just starting out.

7. Axon>Arduino Axon is much more than the arduino although, for your first project, the arduino would be more than enough. Wouldn't recommend trying to make an axon though! If you wish to build an easy board like the arduino, check out the $50 robot. It uses the same microcontroller as the arduino: http://www.societyofrobots.com/step_by_step_robot.shtml

[GearMotion]

If your university teaches the 8085 and 6811-era microcontrollers, it is doing you a disservice.

[MrZappy]

Thanks for the replies. However, I would also appreciate if anyone could further clarify some of the unanswered questions. And on some level, I agree that the university should update their syllabus.

[waltr]

An 8085, I thought these died out years ago. This was in my second computer back in 1982.

On the other hand the 8051 just won't die. It is very popular as a processor core in a good number of devices. For example, the Cypress EZ-USB chips have an 8051 built in and both Xilinx & Lattice offer a 8051 core in VHDL for their FPGAs.

Since you are going for an EE degree you should be familiar with assembler code on a few different processors and processor architectures. The 8051 is not a bad processor to start with but do work with a few others. This way when that NEW one  comes to market you will be able to read its data sheet and know how to wire and program it.

[MrZappy]

I do plan to be familiar with various processors and controllers eventually. However, now I need a starting point to learn as all of these are still quite new to me. Anyway, a quick question, the $50 Robot, in the tutorials, there was a header pin to connect a serial cable to program it. I think it was called the programmer header. What is an external ISP programmer then? I mean in order to program my Atmega8 chip, do I need an external programmer to connect the PC and the motherboard? Because from what I understand from the $50, is that the cable goes into the header and the end end goes into the PC without an external programmer circuit. Please clarify. Thanks again.

[z.s.tar.gz]

The computer is the programming circuit in a way. The programming cable is simply a way to connect serial/usb to the controller.

[billhowl]

8051: an old but very popular controller. The older 8051s are kinda slow: 12 clocks per instruction. Newer 8051s have 6 clocks per instruction up to 1 clock per instruction - make sure you know which because it really makes a difference. The 8051 is made by almost every company that makes microcontrollers which gives you a huge selection. The selection of low pin count devices is a bit limited. Most 8051s have an external memory bus that makes it easy to add memory and peripherals. CISC. Free C compiler.

The Intel 8051 is a single chip microcontroller developed in the 1980s. It has now been largely replaced by its descendants with the Intel designation of MCS51 for the 8051 family.

The Intel 8051 is a Harvard architecture, single chip microcontroller (µC) which was developed by Intel in 1980 for use in embedded systems. now an open standard with many 8051-compatible devices manufactured by more than 20 independent manufacturer, some are One time programable version, and Flash version.

8051 MICROCONTROLLER has no in built A/D Converters but PIC & AVR has it.

The popular 68hc11 is a powerful 8-bit data, 16-bit address Von Neumann architecture, microcontroller from Motorola (the sole supplier) with an instruction set that is similar to the older 68xx parts (6801, 6805, 6809). The 68hc11 has a common memory architecture in which instructions, data, I/O, and timers all share the same memory space. Depending on the variety, the 68hc11 has built-in EEPROM/OTPROM, RAM, digital I/O, timers, A/D converter, PWM generator, pulse accumulator, and synchronous and ansynchronous communications channels. Typical current draw is less than 20ma.


PIC: Slightly less old than the 8051. PIC is a family of Harvard architecture single chip microcontrollers made by Microchip Technology, derived from the PIC1640[1] originally developed by General Instrument's Microelectronics Division. The name PIC initially referred to "Programmable Interface Controller". PICs really shine with their small low pin count devices. Small and very cheap with decent performance. Marketed as RISC but is more like a CISC processor with only a few instructions.

PIC: Pros - easy to avail, cheap, good support, free tools available, variety of ICs available with selectable features
Cons: Not exactly cons, but some people just dont like it. Most hate about PIC is programming it in assembly for the small memory models. You can of course program PICs in C. Microchip do have a free version of their full C package.

AVR: The newest architecture by about 20 years. Designed for a pipeline so has very good clocks/instruction. Many more registers than 8051 or PIC. Good range of devices: small and cheap to fairly high performance. Most RISC of the 3 which makes it the most C friendly. Free C compiler.

The AVR is a Modified Harvard architecture 8-bit RISC single chip microcontroller (µC) which was developed by Atmel in 1996.

AVR: Pros - Most powerful 8-bit architecture, All variants are loaded with features, free IDE and c-compiler, easy support available, Large community of AVR lovers 

Cons: May be difficult for starters, but no cons exactly.   


There are other things to consider as well - RISC versus CISC - Reduced instruction set computers typically combine functions, or speed them up, so they don't take as much time as CISC (complex instruction set computers), thus making them slightly faster for certain operations. And then there's the memory architecture: Harvard versus Von Neumann - You can Google these to read about them, but basically the Harvard keeps instructions and data in separate areas, and Von Neumann combines them in the same area...

Also, speed wise, the top end PIC's are a match for the top end AVR's, if you compare low end PIC's with top end AVR's, then obviously the AVR's are faster. But if you compare top end PIC's with low end AVR's, similarly the PIC's are far faster than the AVR's. However, this isn't to say that RISC is a good thing or a bad thing!, nor that higher speed is always desirable - most microcontrollers will spend the vast majority of their time simply wasting time - probably well in excess of 99% spend in loops and waiting for something to happen.

The Reduced in RISC means simpler not nessesarily fewer. The PIC violates a bunch of RISC rules. PIC is sort of half RISC half CISC. It follows some rules and violates others. The AVR is much better about following the rules even though it has more instructions.

http://en.wikipedia.org/wiki/RISC is a good definition of RISC computers.

Whether or not RISC is a good thing or even if there are any "real" RISC processors is almost impossible to answer because there are so many variables.

8051, PIC & AVR

All are based on Harvard architecture (separated program and data areas). All can be programmed using assembly language and various high level languages. All have similar pricing. The software is not interchangeable between all the families.

In each family there are numerous models that offer a huge range of features. Although the ranges compete with each other, they all offer solutions for many applications. During the early stages of a product development, either of the families might be selected without noticing particular disadvantages with either choice.

8051s and PICs both have their enthusiasts who will claim that one is far superior to the other. Their view is perhaps close to the truth for a simple reason: The PIC fans tend to have far more experience with PIC design and programming and the 8051 fans of course will know 8051s better. It is this knowledge that makes for a specific choice rather than the hardware itself in most cases.

This is the most controversial and disputed question. PIC users will swear by PIC, AVR users will always rant about AVR and then there will be people who will vote for 8051.

You cannot compare microcontrollers, it all depends on our need. Learning and implementing projects on different microcontrollers is fun, but when a real setup needs to be formed, then the choice of microcontroller will depend on the requirement.

If the requirement is of large no. of I/O lines but not many peripherals are required then the basic 8051 is the  best as it cuts down the cost , maybe OTP version can be used.

If 8051 do not stand anywhere infront of the AVR's they should have been obsolete by now, but they aren't, People still use them in their applications. PIC or AVR, this has been another great battle , but it all comes down to requirement. Do you  know that some variants of 8051 can provide 33MIPS, not even AVR or PIC can do that.

Microchip has a huge data base of PIC Microcontroller with lots of support and every day the 8 bit port folio is growing.

It always comes down to requirement, cost,reliability and other factors.


So who is the winner then ?

None actually, it all depends on what best fits your requirement
 
All are equal


 i have worked on MCS51, PIC and AVR. Each has its own properties and positive side.

they cannot be compared......

[Soeren]

Hi,

[...]
PIC: Slightly less old than the 8051.
[...]
Marketed as RISC but is more like a CISC processor with only a few instructions.
[...]
AVR: The newest architecture by about 20 years.

You really need to update your knowledge on the PIC vs. AVR.

Many more registers than 8051 or PIC.
The AVR is a Modified Harvard architecture 8-bit RISC single chip microcontroller (µC) which was developed by Atmel in 1996.

Either you misunderstand the RISC/CISC concepts or you're going religious on AVRs.

AVR: Pros - Most powerful 8-bit architecture,

Clearly, you're going religious on AVRs.
Not a good way to inform a beginner.

Cons: May be difficult for starters, but no cons exactly.   

Most people actually find AVRs (and the entire MCS51 line) the easiest to start with.

[...] if you compare low end PIC's with top end AVR's, then obviously the AVR's are faster. But if you compare top end PIC's with low end AVR's, similarly the PIC's are far faster than the AVR's.

And your point exactly is??

The Reduced in RISC means simpler not nessesarily fewer.

Reduced in RISC means fewer, but not necessarily simpler (actually, each is more complex).

The PIC violates a bunch of RISC rules. PIC is sort of half RISC half CISC. It follows some rules and violates others. The AVR is much better about following the rules even though it has more instructions.

Don't grab these strange postulates out of thin air - substantiate with examples!

Whether or not RISC is a good thing or even if there are any "real" RISC processors is almost impossible to answer because there are so many variables.

But yet you find it OK to go authoritative on the subject, no matter a beginner may take it as the truth?

This is the most controversial and disputed question. PIC users will swear by PIC, AVR users will always rant about AVR and then there will be people who will vote for 8051.

Oh, I believe that I try to give advice from the users perspective and I usually tell them that my present preference is mostly PIC (even if I have used most cores available since the mid seventies).

You cannot compare microcontrollers, it all depends on our need.

And based on your needs, you compare them

If 8051 do not stand anywhere infront of the AVR's they should have been obsolete by now, but they aren't, People still use them in their applications. PIC or AVR, this has been another great battle , but it all comes down to requirement. Do you  know that some variants of 8051 can provide 33MIPS, not even AVR or PIC can do that.

AVR is based on MCS51 and so are several other and as long as one of those is still in production, MCS51 will stay current. The original and first 8051 IS obsolete, but the core prevails.

Microchip has a huge data base of PIC Microcontroller with lots of support and every day the 8 bit port folio is growing.

Not just the 8 bit line. The 16 bit and 32 bit lines, the dsPIC (DSP enabled controllers) and rfPIC (the controllers with build in radio comms), the XLP controllers that runs on "air" are all in a continuous development, with more added frequently - Many of those "special deals", isn't found in the AVRs line IIRC.

i have worked on MCS51, PIC and AVR. Each has its own properties and positive side.

they cannot be compared......

Oh, yes they can (and that's what you do in your entire post), but AVR is for all intents MCS51, so no need to differentiate the two.

[GearMotion]

BillHowl: I thought your post was an informative contribution to this thread and an excellent, generous source of data for the Original Poster. It should help the OP considerably. Hopefully the O.P. ignores the reply to your post as it is S0ren's usual "I know everything and I'm always right so YOU prove me wrong" incessant diatribe. A comment like "AVR is for all intents MCS51" is foolish. There are similarities in architecture, but certainly no instruction set compatibility for any claim to be "for all intents MCS51". I will blissfully ignore S0ren's continuous sputter. It is only good when he can keep his ego in check.

[Soeren]

Hi,

1. The main question I have is the difference between 8051, AVR, PIC and Motorola's 68HC11. What is AVR by the way? I know it is manufactured by Atmel but that's all I know. Only the 8051 and 8085 is within my syllabus. Therefore I am more interested to learn up these two types.

AVR is one of the multiple families that build on the MCS51 core, the same one in the 8051.
Motorolas 68HC11, I wouldn't choose today, it was nice back 15..20 years
Since you're using the 8051 in school, it would give you the most edge to start with that - you can go with other cores later on.
8085 is MCS51 as well, but I wouldn't waste time on that.

Do you know the exact type of 8051 that you will be using?

2. Is it possible to purchase the necessary components to assemble your own 8051 board at home? I plan to invest a little cash to play with the board at home. Do they come in DIP? Because SMD insn't an option as I don't have the necessary skills to solder it on.

It really depends on which exact 8051, but you could allways build it on a matrix board or make a real PCB yourself.
But first things first - Which 8051 are we talking about?

3. Can the 8051 drive motors like the PIC and AVR? Basically, can it do what the other chips can do? What about 8085 then?

There will be some differences in the features of each, but that goes within a single controller line as well. They can all control other circuits, motors etc. through their I/O pins.

4. The language to learn. I understand some language are chip specific. So, how do I go about learning them. I read through the sticky at the start of this forum regarding 8051. It mentions learning up C and using Proteus for simulation. Is this the standard way?

For school work, you will probably have to use at least some assembler and likely C and if you haven't got any other preferences, just stick to that.
You can use a simulator or you can go with the Crash & Burn method.
A simulator will add to the things you have to learn, so perhaps save it for now, you have quite a bit to learn as it is allready.

5. Is there any noticeable difference between Intel's 8051 and Atmel's 8051? I understand the technology came from Intel first but what I want to know is whether they are interchangeable. Because I think Intel's 8051 only comes in SMD form whereas Atmel's 8051 comes in DIP. I want to get something that I can experiment at home.

Again, you have to be specific about which, but in general, the differences are not that large - I'll still advice getting the exact device that you are supposed to use in school, as this will really boost your confidence in it.

6. I am also interested in robot building. Can I provide the brains of the robot in the form of 8051 or 8085? Because those are the major stuffs that I learn about, I would prefer to use as opposed to PIC. Besides, I heard the 8085 has much more memory capacity as it uses external RAM. Is this true? And can I drive motors with 8051 and 8085? More importantly, can I build the 8085 in the first place?

Any controller can be a robot brain.
The 8051 is not a microcontroller, it's a microprocessor lacking ROM, RAM and a lot of other stuff, which has to be added as peripheral equipment. The program will have to go in an (EEP)ROM and you will need equipment to program EPROMs and, if using UVEPROMs, an UV eraser - it's just too much bother and too expensive.
Never mind the amount of addressable memory, it will be some time before you fill up a a few kB and any controller can be made to control eg. an SD card storage (or even a hard drive) to load from, so space is not really a limiting factor.

7. I am thinking of purchasing an Arduino or an Axon but I would prefer if I can make them on my own rather than buy them cause delivery would be a problem. Anyway, what's the difference between them? Is the Axon powerful enough to support a robot in a competition?

Anything can support a 'bot in a competition, it's the person building and programming it that needs an upgrade if it goes bad.
Start out with what can help your studies and start out with realistic ambitions. When you're good at one core, the next will be a piece of cake to learn in comparison.


If you post the exact type number of the 8051 here, you could get the help needed to make a board with LEDs and buttons etc. that will help you further your studies.

You are best off to learn the ropes before tying them into a robot.

[Soeren]

I will blissfully ignore S0ren's continuous sputter.

Yes, I see that you do   

[MrZappy]

Thank you! Soeren and billhowl! I really appreciate the replies given by the two of you. I can say that I have acquired some useful information from your posts. Well, Soeren, I am not sure exactly on which 8051 I will be using but I will find out. I didn't even know that there are types to begin with. So what should I be looking for anyway? An example would be nice. Well, about the 8051 requiring the program to be inside the EPROM. Are there any cheap alternatives burn the program in other than UVEPROM? And I know you people say forget about the 8085, I get that a lot but unfortunately it is within my syllabus and I have to learn assembly to program it. So, I want to know if the assembly language are the same for all chips of a particular family? Can the 8085 assembly language be used for 8086 and 8088? Lastly, regarding the programmer circuit for the AVR chip, I am still confused as to why I need one to program my ATmega8. The $50 robot clearly doesn't have one. It just connects the programmer header to the serial port of the PC and programs it. Then why all the different types of programmers are required?

Well, sorry if I asked one too many beginner's questions. I am really really excited about electronics and believe or not, I spent the last couple of weeks poking in the dark trying to learn up micro-controllers without getting anywhere.... until now. I am really glad I found this site. Thank you!

[TrickyNekro]

I will blissfully ignore S0ren's continuous sputter.

Hey, he is actually helping a lot around... and that's sounds a little offensive for a guy that has more experience
than the two of us together. At least considering the years he's been around...



And about the AVR - PIC issue... I haven't used PIC much...
But AVRs are come with a free IDE with has many many tools in it...
Maybe PICs did have some nice peripherals sooner than the average available AVR...
But then again I swear for AVR... so I'm a little bit religious over the matter....

Still, I'll mention some bad things about AVRs...
I heard, and I say I heard... that sometimes may not be the type of microcontrollers you want in heavy industrial places
Although, there are the automotive AVRs that are made tough... or at least tougher...
But I don't think that you might be actually switching some life critical high voltage relays 10cm away from the core....
So... f the hell of it....  

AVRs are nice... and cooler cause official programming tools are coming in very cheap...
Plus you don't need that ridicules 12V supply for programming... truth be told...

[TrickyNekro]

Lastly, regarding the programmer circuit for the AVR chip, I am still confused as to why I need one to program my ATmega8. The $50 robot clearly doesn't have one. It just connects the programmer header to the serial port of the PC and programs it. Then why all the different types of programmers are required?

wow wow wow... it's not just a serial cable... It has something in there you know... Maybe a simple JDM programmer...
maybe a more complex one... but certainly there is something in there....

[MrZappy]

http://www.societyofrobots.com/step_by_step_robot_step3C.shtml

Well, I thought in that picture, there was only a serial cable connected to the Atmega8 right? The other headers are for the I/O. But I don't see any external programmers.

[GearMotion]

I will blissfully ignore S0ren's continuous sputter.

Hey, he is actually helping a lot around... and that's sounds a little offensive for a guy that has more experience
than the two of us together. At least considering the years he's been around...

And yet with all of that experience he has been taught by someone incorrectly, or came to the incorrect conclusion on his own that the AVR is from the MCS51 family. It is too bad that he bashed so much of Billhowl's post and then continues conveying erroneous information. Claiming passive-aggressively that others shouldn't be "authoritative on the truth" in order to be perceived as "right".

I find it unfortunate that he has to trash a good post in a poor attempt to make it look like his opinion is more "right". I called him out, he did nothing to prove his assertion involving register-based cpus. I just wouldn't want Billhowl or anyone to be discouraged from posting just because every one of their points were unnecessarily and thinly rebutted by someone with ego issues. Unfortunately he will continue to act unchecked. Unfortunate for us all.

ETA: Billhowl - sorry if this got ugly. I just thought you had put too much effort in your post to have it unnecessarily sniped at. Such a thing raises my hackles. You deserved better treatment.

[Razor Concepts]

http://www.societyofrobots.com/step_by_step_robot_step3C.shtml

Well, I thought in that picture, there was only a serial cable connected to the Atmega8 right? The other headers are for the I/O. But I don't see any external programmers.

There is more stuff going on in the serial cable connector.

[billhowl]

http://www.societyofrobots.com/step_by_step_robot_step3C.shtml
Well, I thought in that picture, there was only a serial cable connected to the Atmega8 right? The other headers are for the I/O. But I don't see any external programmers.

Read the step 1 on the optional parts : there is a  AVR STK Serial Port Dongle Programmer from SparkFun.com
and this is the AVR-PG1B schematic

[GearMotion]

Here is a link to a blog to build your own with a 6-pin header:

http://circuitgizmos.com/wordpress/?p=452

[z.s.tar.gz]

I just modified my dongle programmer today to adapt it to 6 pins. It was very easy and I recommend it if you already have one.

[TrickyNekro]

10 pin are to be considered with longer cables... but aren't obsolete...
Most Atmel official products actually favor the 10pin ISP...

I would recommend an adapter to a total conversion.... 

[cyberfish]

Atmel started by making MCS51 MCUs, but AVRs are a completely different design from ground up that has no more ties to MCS51 than any other MCU. It's a lot more RISC (simpler instructions that do less, where the speed is made up by allowing the device to be clocked faster), and has a lot more registers (the register banks thing in MCS51 is a pain to use, and I'm fairly sure AVR doesn't have that).

The AVR instruction set (http://en.wikipedia.org/wiki/Atmel_AVR_instruction_set) bears no resemblance to MCS51's.

[Actives]

AVR is more faster i think, one clock per one instruction

[cyberfish]

Some Silabs 8051 are one clock per instruction, too.

Most take more, though.

For AVR, most instructions are one clock.

[Webbot]

Re the 8085, 8088, 8086 ..... and trying to use 'everyday' language

I have an old electronic 'cook book' for 8085 published in 1981 ! That may be why others have said that if you are still being taught this then it is a 'disservice' !!

If memory servers (after 30 yrs) - the 8085 was the forerunner to the others: 8088 had an 8 bit bus and the 8086 had a 16 bit bus and was therefore faster. These then became the '286 and then the '386 etc etc that most PC users will be familiar with if 'Intel Inside' means anything.

Code written for the 8088 will also work on the 8086. The opposite also applies - if you don't use any 8086 specific assembly commands. Code for the 8085 is also similar to the others but its amazing your guys can still buy them !!

This generation of processors were aimed at home computers and then business computers - they aren't micro-controllers. They had zero 'on board memory' and so you had to add external memory cards, hard disk controllers, video cards etc - ie build an entire computer around them. As time went on they became bigger and more complex chips that could support more complex instructions (including floating point maths).

The advent of RISC (reduced instruction set) chips took the opposite view.... Make the chips VERY basic with only a few instructions. This meant the silicon design was much simpler, cheaper and the device was a lot smaller. They require more programming instructions to do the 'same thing' but since the architecture is simpler then they can be run at much faster speeds, generate less heat and hence consume less power. The original RISC chips were created by Acorn Risc Machines (ARM) for Home Computers like the Archimedes but are now found in just about every mobile phone on earth. Apple now want to buy the company! But thats another story.

So all of these devices are 'micro processors' - they just run code using program/data memory that is external to the chip. They dont have any onboard hardware to do things like PWM, Uarts/Modems, I2C etc etc. You had to add extra electronics to do that. On their own they cannot achieve anything. Its a bit like saying that they are the engine of a car - it can start up, run, but not actually achieve much unless you add wheels, steering, brakes etc etc.

Then came 'micro controllers' where you have a processor + memory + features like PWM/UARTs etc etc all built onto a single chip. These are like a complete car (albeit a 'mini'). You can do something useful with no extra hardware at all (ok - maybe a few capacitors). There is even a project out there where people are using microcontrollers to simulate an entire 1980's home computer - at a fraction of the cost and a fraction of the size.

Sorry if this is a bit simplistic - but hope it adds something for the original poster! I was always more of a 6502 person myself

[MrZappy]

Wow! This board is really helpful. Thanks a lot. Right now,
I am trying to find the necessary components to build my own 8051 system. Can anyone point me in the right direction regarding the schematics?

I found this schematic. Can anyone take a look at it and tell me if it's any good? And I am a bit confused about part U11. It is connected to port A0-A7 but parts 14, 15, 16 all have port A0-A7. Which component exactly must I connect it to? And it has an 8k RAM and a 32k RAM. Does it mean that this system has 40k of RAM? Can I add more to it for an upgrade?

http://roger.trideja.com/8051/sch8051.gif

[Soeren]

Hi,

Lots of 8085 material
A 8051 system