How to connect two 8085 processors?

[bader]

help in muliprocessors

hi....
I have a project in my college to connect two processors (8085)
but i dont have any idea how to make the first processor to communicate with
the seconde processor to do a useful job ....
so...... where can i get some help

 

[DigitalScholar]

Re: help in muliprocessors

Multiple processors may need to be connected together for applications which are intense and you have reasons to believe that a single processor cannot be able to handle the tasks well. So what sort of application do you have in mind. ? Or you just want to connect the two for the sake of experimentation.

For experimentation case, you can just connect the interrupt lines of the processors and do something in each processor when its interrupted by the other.

 

[IanP]

Re: help in muliprocessors

Difficult to understand why your collage still is involved in ths antique chip.....
Anyhow, I see two options:
1. using 8255 (24 DIOs) for each microprocessor for 8-bit parallel communcation with handshaking (Port A in mode 2)
2. using 8251 (USART) for serial data transmission.
In both cases you may use command-response protocol.

 

[bader]

Re: help in muliprocessors

thanks.......
we use 8085 because its very simple
and we need to connect two 8085 by shared memory not by port
thanks again....

 

[IanP]

Re: help in muliprocessors

So correct me if I am wrong..
Both 8085 cpus have their own program memories (ROM or EPROM) and you would like these 2 systems to share a data memory (RAM). Is it true ?

 

[bader]

Re: help in muliprocessors

you are right......
but the problem is how can i make the first cpu synchronize its work with the seconde
one.........

 

[IanP]

Re: help in muliprocessors

Maybe you don't need to synchronize both microcontrollers..
If you use Tri-state non-inverting buffers for address lines and 8-bit Tri-state non-inverting transceivers for the data bus you can connect both systems to one RAM.
What you need to do is to conncect 2 I/O lines between both 8085s and this will be your synchronization: if CPU1 asserts one of these lines LOW the CPU2 will have to wait before accessing RAM for as long as this line is LOW, and opposite way around, CPU asserts the second line LOW and CPU1 has to wait..