8088 / 8086

[mstechca]

I bought an 8088 IC, and when I looked at the datasheet, it shows that 8 data lines can be used as address lines. In simplest terms, exactly when do I treat the lines as address lines, and when do I treat them as data lines?

 

[Nigel Goodwin]

I bought an 8088 IC, and when I looked at the datasheet, it shows that 8 data lines can be used as address lines. In simplest terms, exactly when do I treat the lines as address lines, and when do I treat them as data lines?

To make the processor smaller the data and some of the address lines share the same pins, you have to switch between data and address lines, and latch the address into external latches.

An 8088 is a micro-processor, not a micro-controller, you will need a large amount of extra chips to be able to use it - latches, RAM, EPROM, I/O chips, oscillators, reset generators - it's not a trivial task. You also appear to be doing it 25 years too late! :lol:

 

[electronist]

As long as your Address latch Enable (ALE) pin is activated you will have to consider the lines as address lines. During all other times these lines behave as data lines.

 

[williB]

I bought an 8088 IC, and when I looked at the datasheet, it shows that 8 data lines can be used as address lines. In simplest terms, exactly when do I treat the lines as address lines, and when do I treat them as data lines?

as electronist said the ALE pin (tells you/and is used to signal your support circuitry) when the lower 8 pins of the address bus are in fact addresses

look at the bus timing diagram..the ALE goes active on the falling edge of T1 cycle..

 

[mstechca]

Thanks.

Nigel, I'm not trying to make a super-gigantic 8088 computer system.

I want to be able to wire an 8088 to an LCD, some memory modules I have lying around, and to a data source (eeprom or my parallel port of my PC).

I know an 8088 is over 25 years old, but since I know alot about machine code, there should be no problem using it, once the circuitry is complete.

I bet an 8088 is cheaper than a '386 or '486. Also, Why would I jack up to a newer processor if a) more new processors dont come in a DIP package, and b) more new processors come with extra instructions added to the instruction set that I dont need, and c) new processors may have more pins I need to worry about. ???

 

[Nigel Goodwin]

Thanks.

Nigel, I'm not trying to make a super-gigantic 8088 computer system.

I want to be able to wire an 8088 to an LCD, some memory modules I have lying around, and to a data source (eeprom or my parallel port of my PC).

You don't seem to have looked into what is required to make it work at all!, as far as not even knowing that the address lines are multiplexed?.

What you want to do is VERY simple using a PIC, and would take one small cheap device, easily and cheaply programmed - a similar 8088 system is probably going to require chips in double figures?, or certainly getting close to it!. Do you also have an EPROM programmer to blow an EPROM for the program you need to write?.

As I mentioned before, 25 years ago you might have had to do things this way (although the 8088 wouldn't really have been a good choice then either).

If this still just trying to get an LCD to work from your PC?.

 

[mstechca]

If this still just trying to get an LCD to work from your PC?.

Not exactly. That problem was fixed.

Here is what I assume with an 8088 (correct me if I am wrong):

#1. each clock cycle applied to the 8088 will increase the address by 1.
#2. When a particular address is reached, the 8088 will determine with the read and write signal lines whether it receives or sends data.
#3. The ALE signal is activated the same time as the read or write lines which makes the ADx lines, data lines.

But just to start off, I want to make it work with my LCD and my computer's PC port. After that, I will introduce new chips into my "mini computer".

 

[mstechca]

I thought an 8088 was a good choice because I have extensive software programming experience with it and it is well known.

as for the PIC's, They might be more expensive because they are "microcontrollers". right?

 

[Nigel Goodwin]

I thought an 8088 was a good choice because I have extensive software programming experience with it and it is well known.

I'm all for using a processor you're familiar with, but using multiple chips and a fair amount of money, to do such a simple job, doesn't make much sense?.

Have you got a list of the minimum chips you will need to get your smallest working 8088 system?.

as for the PIC's, They might be more expensive because they are "microcontrollers". right?

PIC's cost VERY little, depending on the particular one used, they can be under $1.00 - even the expensive ones are only a few $'s. It's often easier to use a PIC than a 555 timer, and it doesn't cost much more - but can give accurate timings from microseconds to years (or higher!).

 

[upand_at_them]

From Jameco:
8088 microprocessor.....$10.99
PIC16F628 (far far superior and easier).....$3.69

PICs can be purchased for even less than that.

Forget the 8088; you're wasting your time and money.

Mike

 

[Nigel Goodwin]

PIC16F628 (far far superior and easier).....$3.69

I think that's a little harsh! :lol:

You can't really compare them as they are very different devices, the PIC is a micro-controller, and the 8088 a full micro-processor - the 8088 is intended to be a small part of a large complete computer system, where the PIC on it's own is a small complete 'computer system'.

 

[mstechca]

Sayal Electronics Canada:

8088 - $3!

I saved probably $1 or $2.

My god, America is expensive to me. Thats cuz I'm canadian!

 

[samcheetah]

Sayal Electronics Canada:

8088 - $3!

I saved probably $1 or $2.

My god, America is expensive to me. Thats cuz I'm canadian!

even then an 8088 isnt the only thing you will be buying. you will have to buy a couple of other ICs to make it working as it has been told to you before.

doing microprocessor projects with pre built kits looks good at the college level but i seriously dont recommend doing projects with microprocessors these days. microcontrollers are far more easier to use.

 

[upand_at_them]

PIC16F628 (far far superior and easier).....$3.69

I think that's a little harsh! :lol:

You can't really compare them as they are very different devices, the PIC is a micro-controller, and the 8088 a full micro-processor - the 8088 is intended to be a small part of a large complete computer system, where the PIC on it's own is a small complete 'computer system'.

I should have added: "for what he wanted to do."

Mike

 

[electronist]

I feel the 8051 version of chips are the cheapest. We get them for around 1/2 a dollar here in India. Flash versions are also available.

 

[panic mode]

If using x86 system is what you want why not look into PC104 modules?
they are everywhere and in ALL sizes (cpu and memory-wise).
here is one using celeron:

**broken link removed**

take a look at the picture and if you think you can do same PCBs at home put all chips and still keep the module price under $20-30, send me your address