Building an 8088

[Sausages]

Hello all!

I've been set an assignment recently to build a working 8088 system. Now I've spent a few hours reading up on the subject and I think I have most of it down.

I'm having a few problems with the 16-key keyboard/display interface unit and the programmable I/O interface.
For the keyboard I'm using a 4x4 key matrix, the output of which is connected to a 8279. The SL pins of this are connected to 2 3-8 decoders ( one of which is fed into the matrix ( pins 0 - 3 ), the other being fed into the LED digit display )

The interface I'm using is the 8255, I've configured this to be :

PA - Input
PB - Output
PC - Output

We've been asked for a 8/in 16/out interface in the brief

My question is to connect these two devices together, am I right in thinking that I will use the output of the 8279 ( PINS OUTB0-3 and OUTA0-3 ) to be the input of the 8255 ( Pins PA0-7 )??

Am I right in thinking that PB and PC ( outputs ) are both connected to the address bus of the CPU.

Also, are the A0 - A7 pins of the 8255 connected to the input of PA0-7?

The NAND gate bit still confuses me though...


edit:I've made a little picture to try and detail what I want to do. I've left out the 74318 connections for the control lines of the Ram and EPROM, and the memory itself for simplification. I know it's a rough diagram but I hope it's okay.

The brief for the assignment was:

48K Bytes of EPROM for programme memory (choose the components that will give you the exact size of memory).

12K Bytes of RAM for Data memory (choose the components that will give you the exact size of memory).

A Keyboard/Display Interface unit (should support an 8-digit LED display and a keyboard of 16 key switches).

A programmable I/O Port (8 I/P lines and 16 O/P lines, mode 0), Give the right code that will initialise the chip to the required mode.

As you can see I'm still stumped as to the A0 and A1
For the EPROM and RAM I plan to use combinations of 16k, 8k and 4k.as said he wants exact values

Thanks!!

 

[Nigel Goodwin]

"It's just a jump to the left......."

 

[Sausages]

Hmmm I presuming that means I'm goosed......

 

[ericgibbs]

Hmmm I presuming that means I'm goosed......

hi,
I have just dug this out, its one of my very old cpu designs. circa 1989!!!

Its based on the Z80. which is the older sister to the 8088.

It should give all you need to know ref the 8088 and 8255.

Enjoy...

 

[blueroomelectronics]

"and a jump to the right..."

 

[Sausages]

hi,
I have just dug this out, its one of my very old cpu designs. circa 1989!!!

Its based on the Z80. which is the older sister to the 8088.

It should give all you need to know ref the 8088 and 8255.

Enjoy...

Thank you sir, you've just saved my bacon I had a bit of that from my notes but that diagram is invaluable

 

[Nigel Goodwin]

"and a jump to the right..."

At least someone recognised the line!

(apart from the second line is 'step' and not 'jump')

 

[ericgibbs]

At least someone recognised the line!

(apart from the second line is 'step' and not 'jump')

Rocky Horror Show!

Transalvania ?????

Is my prize in the post.?

 

[Nigel Goodwin]

Rocky Horror Show!

Transalvania ?????

Is my prize in the post.?

Still missed the point! (and the title).

 

[ericgibbs]

Still missed the point! (and the title).

In that case, please enlighten me....

 

[Nigel Goodwin]

In that case, please enlighten me....

The song is called "Timewarp", which is what we appear to have fallen through!

 

[ericgibbs]

The song is called "Timewarp", which is what we appear to have fallen through!

Yep, thats the one, just couldnt recall the damn name, having a senior moment.

Thanks, must dash, got to reorganise my sock drawer....

 

[mneary]

Be careful using that Z80 diagram. They do have a lot in common (same era), but a very important difference is that the Z80 does not have a multiplexed address/data bus while the 8088 does. So the Z80 hookup of address bus won't work on the 8088.

 

[mneary]

This site has a project much like the one you're building. intel used to have some nice app notes for this architecture, but it looks like they removed these documents from their web site almost ten years ago. Your school should probably try to be in this century also.

My question is to connect these two devices together, am I right in thinking that I will use the output of the 8279 ( PINS OUTB0-3 and OUTA0-3 ) to be the input of the 8255 ( Pins PA0-7 )??

Probably not. The 8279 can connect directly to the CPU's data bus using its own chip select.

Am I right in thinking that PB and PC ( outputs ) are both connected to the address bus of the CPU.

No. These are your 16 bits of required output. The 8255's data pins (D0-D7) connect to the CPU's data bus. A0 and A1 connect to the corresponding bits on the CPU's address bus.

Also, are the A0 - A7 pins of the 8255 connected to the input of PA0-7?

No, PA0-PA7 are your required 8 bits of input. Your 8255 should not have A0-A7 pins.

[edit] clarified some descriptions [/edit]

 

[blueroomelectronics]

How about a "Captain Dunsil" reference?

 

[Nigel Goodwin]

How about a "Captain Dunsil" reference?

Had to google that one!

 

[ericgibbs]

Had to google that one!

Me too.!

 

[Tacan]

Thats Star Trek, the ultimate computer episode i believe. I love TOS.

 

[blueroomelectronics]

Thats Star Trek, the ultimate computer episode i believe. I love TOS.

That's right, Spock referring to Kirk "Dunsil, Doctor is a term used by mid-shipmen at Starfleet academy, it refers to a part that has no useful purpose!"

 

[Super_voip]

I once owned a book "The 8088 cookbook" and it showed how build an 8088 system from ground up. It was this book that made me realise that micro-controllers were the way to go. I don't see it using Google so it may have vanished. It started with the bare minimum and built up, using diodes then EPROMs for programming.