[51] regarding the architecture problem

[r@wboom]

hello there,
i want to understand if i interface the eeprom to 8051 then will it be a von neuman architecture.
can anybody help me to understand the basic of this.

 

[Kurenai_ryu]

please attach reference circuit... (what circuit are you plannig to use?)

there are two ways to connect external memory to a common 8051...

both ways uses Port0 as A/D[7..0] and Port2 as A[15..8] and uses the ALE pin to latch the Address from port0

but,

1. you can add external PROGRAM Memory by connecting the PSEN pin to the EEprom RD (the eeprom WR is not used and should be connected to Vcc with a pull-up)

2. you can add external DATA Memory by connecting the port3 pins RD and WR to the corresponding ram RD and WR (you can use the eeprom as external data memory but you would need special treatment to actually write some data on that eeprom)

...

So basically you still have a Harvard architecture with a program region up to 64KB (in most 8051s) and a data regin up to 64KB too (so the microcontroller have a total access of 128KB tops in both program and data)...

but as you didn't attached a circuit, you can consider that some people 'combine' the PSEN and the RD from the microcontroller to read a single memory (your RD eeprom) effectively having only one memory for both program (wth the psen signal) and data (with the rd signal) values... making a so called Von Neuman architecture...