Multiprocessor 8052 Interfacing

Dear ALL,
Does anyone can help me about interfacing multi 8052 via serial communication...
I know it's possible with mode 2/3 serial comm, but how about bus connection?

I did a system so meany years ago . It consisted in several handhelds being polled with a number ID if the handheld we wanted to conctac was there ,it will reply and the the master will get the data out of it . The remanining will go hi impedance and go back to sleep . Evrey time we wanted to talk to any one .we will raiose CTS or another signal that will wake them all up .Then they they will listen for the ID broadcasted my the master . If the ID matched the handheld it will signal RTS .to the MASTER .. otherwise it will go back to sleep

It really worked very nice for several years and hundreds of comunication cradles produced .. Now chips from cygnal allow this type of syncronous MBUS i think that they called .so check them out

www.cygnal.com

Thanks Eltonjhon..
I've little confused about txd and rxd line connection between master and slave or viceversa...
May be you can describe more detail about bus connection ..

Rgds,

The TXD cpu1 goes to the RDX ..cpu2 so if you have a MASTER unit .The master TXD will go to all cpus RXD (is said BROADCASTED to all) .. but because some unit my crash or go bad .. Is better to connect the MASTER RXD to as many line BUFFERS ( line drivers )to as many SLAVES units you have And this driver feeds the RXD line if each micro . Now . in this configuration . All SLAVES units TRXs are connected to just one driver going to THE MASTER RXD .
They can be ligically added i mean ORED .. but dont forget only one transmit a the time . This type of muliprocessor serial connection
is of the type of MASTER and SLAVES also called FARMING .. one cpu is in charge of getting the data( FARMING) or affecting the tasks ..is simple and works ok !

I can understand it Eltonjhon.... How if cpu1 become slave and cpu2 become master? I mean how about the bus connection if the CPU can act as a master and slave (cascading connection) ?

Does anyone know about the idea of multiprocessor communication as follow :

1. CPU1 Serial0 port connect to PC serial port,
2. CPU1 Serial1 port connet to Multiprocessor Communication Bus.
3. CPU2 Serial1 port and other CPU connect to Multiprocessor Communication Bus.

No .No in the FARMING CONFIGURATION . YOU SELECT the wich one is the MASTER .. and it will never change .. !

Listen doing multiprocessor communication with serial interface can be a nighmare .. It was meant to comunicate bewteen only two devices . Look a the Cygnal 51 chips they have a MBUS but is syncronous and allow MULTIPROCESOR comunication . Doing it with a serial asyncronous connections can only be done with tokens and it will be very heavy in protocol .Farming is easier because all units are slaves so they don't request the comunication .. But there is one wich is a MASTER that poll them to send or receive data !

Ok... i get it all.... i'll cek the cygnal 51...

"FARMING CONFIGURATION" is not suitable to my design specification...

Do you have another solution ?

hifni said:

Dear ALL,
Does anyone can help me about interfacing multi 8052 via serial communication...
I know it's possible with mode 2/3 serial comm, but how about bus connection?

Click to expand...

Did you mean any serial interface? Then just add RS485 converter and you will get RS-485 network. BTW, some uC have special mode of serial I/O port with automatic address recognition, like AT89C51RD2/ED2 from Atmel. Also, they have embedded support of SPI, which is also serial interface and also can be used for multi-uC connection.

Ace-X.

Hi Hifni,
I know this is very late, but I just saw the message. I was thinking about the same thing: several PEER TO PEER 8052s sahring a single bus.
This idea I saw in a book called "the final word on 8051". It was as follows:
To multiplex two signals so that you can choose which one goes into the 8052 RXD do this: combine each input with one of general I/O pins on an AND gate, take the o/p of the and gates and combine them with an OR gate, the O/P of the OR gate goes into the RXD pin.

To clarify: you want your 8052 No1 to receive from either the PC or 8052 No2:
take 8052 No2 TXD and P0.0 on an AND gate
take the PC TXD and P0.1 on an AND gate
take the O/p of the two and gates on an OR gate.
The operation will be as follows:
If you put a zero on P0.0 then 0 AND No2 TXD = ZERO
If you put a one on P0.0 the 1 AND No2 TXD = No2 TXD
Thus to listen to one of the inputs (PC or No2) put a 1 on its P0 pin, and a zero on the other input P0 pin. the output of the AND gate will be whatever the source (PC or No2) is saying, the o/p of the other AND gate will be ZERO, "Zero" and "Message" go into the OR gate with the output being "Message" into the RXD pin.
the above can be extended for more than two inputs.

P.S. Whoever said a picture is worth a thousand words was damn right !! I wish I could send the schematic from the book (which you can find online by the way, try google).