port expanding of at89c51?

[buts101]

hello guys...

i need to whole lot of device to at89c51..lcd,keypad,cdrom,ram,..I like to know what are good ways to expand port? I know these possibilities:
1. 8255 ppi (i can't find it in market)
2. using another mcu and serial communicating with master mcu
Plz guys, which one is faster?

thank you
Buts101

 

[memarian]

Dear,
use 82c55,for buying that goto Farnell : they have CS82C55A & CP82C55A series

from INTERSIL in 5&8 MHz versions,DIP & PLCC Packages.

goto www.farnell.com select your country and search 82c55! That's All!

I also think it is easier and faster because it is a parallel interface that can work

up to 8MHz Clock(up to 64 Mbit,if you have an Ultrafast uController!).

Good Luck!

 

[x_zoli]

Hi,

You can map parallel I/Os in the xdata memory space using latches (74HC373, 573) for the outputs and buffers (74HC245) for the inputs.

 

[IanP]

The 82C55 is a very good option, however, there are some other options ..
Using just 2 microprocessor pins for Data and Clock and a few (or none) pins for address you can connect several I2C port expanders ..
Here are some examples:
PCF8574 - 8-bit
PCF8575 - 16-bit
MAX7311 - 16 -bit
MAX7314 - 18 -bit
Of course, communication with these devices is slower than through the 8-bit parallel Address/Data bus, but if you can't get hands on the 8255 then these bit-addressable port expanders can be quite interesting alternative ..

Regards,
IanP

 

[Shani]

Assalamo Allykum !

I think the 8255 is the best option for expanding the I/O Ports.

Allah Hafiz

 

[yogi]

use 74374 with some decoder(if you require)for more expansion. See how I expanded parallel port for inputs and outputs, use the same technique
**broken link removed**

Bibin John
www.bibinjohn.tk

 

[baghery]

hi:
you can used the decoder and latched chips