coding problem for external SRAM interfacing with p89v51rd2

[avineshb006@gmail.com]

Hi
I need to WRITE and READ some data to and from a single SRAM using an p89v51rd2 micro-controller. i had used the xdata initialization to the variable for the particular address like

unsigned char xdata var _at_ 0xD200

hear i want to read and write the data which is stored from sram of (128K*8) memory, that data has need to shown on hyper terminal by using serial communication, and i am having the hardware which is working perfectly by some other previous old code which is not implemented by me.

Please help me with the interfacing circuits and necessary codes to work under keil c ide.

 

[sky_123]

Given that a 128x8 SRAM has about 32 pins, I don't think you've got enough pins on that microcontroller
to do much more than drive an SRAM.
You've got no external address or data bus so you'd need to write code to sequence the port bits to match
the read and write chart in whatever SRAM model you choose. The datasheet will usually tell you how to
set the address and data bits, how to select the SRAM and what pin to pull to read or write.
Why not try to prototype this and see how you go.

 

[bigdogguru]

While it is certainly possible to implement a custom banking scheme, without it I believe you will be limited to 64KB of External Storage.

Typical interface:



Reference: P89V51RD2 Datasheet, Section: 7.1.2 Data RAM memory/7.1.3 Expanded data RAM addressing, Page: 14

7.1.2 Data RAM memory

The data RAM has 1024 bytes of internal memory. The device can also address up to
64 kB for external data memory.

Typical 512kB Banking Scheme:


AP0824 Program Memory Expansion by using the Bankswitching Capability of the C5xx/80C5xx Family


BigDog

 

[avineshb006@gmail.com]

Thanks bigdogguru & sky_123

hear i need to interface the external sram (AS6C1008), which is having the (128K*8) size of memory.
i jus tried with using the xdata variable in the banking of memory locations..
hear i am uploding the code which is i am triying to load on my hardware, please go throw that and tell if any wrong in this.......