accessing of external data memory

[bleach]

can u please explain me how the accessing of external data memory happen with graph if possible. in μc 8051

thanks

 

[3v0]

Homework ?

 

[bleach]

replay

no its not homework, i am having exam next week and having some doubt about the process



thanks

 

[3v0]

Either check books in you library or google for it. If the instructor is going to ask about this either he provided a handout or it is your book right ?

 

[bleach]

its not that much clear in my book, and i read in other book, i couldn't understand so that's why am asking.

regard

 

[colin mac]

AD0 to AD15 is the address bus. AD0 to AD7 is also the data bus.
The address is put on the address bus. The latch is enabled. Then the data is put on the data bus and read by the micro.
**broken link removed**

 

[bleach]

AD0 to AD15 is the address bus. AD0 to AD7 is also the data bus.

The address is put on the address bus. The latch is enabled. Then the data is put on the data bus and read by the micro.

**broken link removed**

here i have address from AD0 to AD7 connected to the latch circuit and at the same time to the EPROM, so in which one the address will be put.
what i know is the address A0 - A7 is low byte and A8-A15 will be high byte, but why?
how the data will be put on the data bus (do u mean it will be put by the EPROM?

thanks

 

[colin mac]

here i have address from AD0 to AD7 connected to the latch circuit and at the same time to the EPROM, so in which one the address will be put.

The low byte of the address goes though the latch. The high byte is connected directly as you can see. Port 0 then becomes the data bus and reads the output byte from the EPROM.
**broken link removed**

what i know is the address A0 - A7 is low byte and A8-A15 will be high byte, but why?

So the address bus is 16-bits wide.

 

[bleach]

thanks

Port 0 then becomes the data bus and reads the output byte from the EPROM.

do u mean port0 send only address in low byte to the latch not data
and after latching the address it read the data from EPROM

i mean how p0 becoum data bus and why send address first then data,?

also

So the address bus is 16-bits wide.

what do u mean....

thanks

 

[colin mac]

do u mean port0 send only address in low byte to the latch not data
and after latching the address it read the data from EPROM

Yes because an EPROM can't be written to. Read the link I gave you, it describes accessing both external code and data memory.

i mean how p0 becoum data bus and why send address first then data,?

The address of the memory location needs to be put on the address bus or you won't be able to access it. Google "address bus".

what do u mean....

It's a 16-bit address bus. It can't be simplified any more than that.