interfacing 2.7V flash memory with NXP P89V51RD2 which is 5V

[nikhil_sutar]

hi,
i wanna interface a spansion flash memory with a nxp P89V51RD2 using spi protocol but m facinng some problems can anyone help?? is it possible to interface a 2.7V device with a 5v micro controller???

 

[nandhu015]

You can use a simple voltage divider using 2 resistors to interface the memory

Nandhu

 

[bobsanjose]

Re: interfacing 2.7V flash memory with NXP P89V51RD2 which i

Hi,
why don't you use the pin compatible P89LV51RD2 which is a 3V device?
If other parts of your circuit really need the 5V, you have to scale down the voltage like Nandhu suggested for all signals originating from the MCU. You also need to make sure that the min high level of your external flash memory output is high enough to reach the minimum high level of the MCU for Vin-high

hth, Bob

http://ics.nxp.com/products/80c51/datasheet/p89lv51rb2.p89lv51rc2.p89lv51rd2.pdf

 

[nikhil_sutar]

Re: interfacing 2.7V flash memory with NXP P89V51RD2 which i

thanks both of you,
but my main objective is to use RD2 in SPI mode, m already using vtg divider ckt for SCK, CS and SI pin, but problem M facing is for SO pin which i have to return from slave which is 2.7V to master which is 5V...

Added after 7 minutes:

hi bob,
thanks for suggestion but i think P89LV51RD2 doesn't have an in built SPI,, correct me if m wrong

 

[nandhu015]

The same voltage divider will work for SO also. If you face problems use a transistor(but you will get inverted signal).

Nandhu

 

[nikhil_sutar]

Re: interfacing 2.7V flash memory with NXP P89V51RD2 which i

sir,
i tried with the voltage regulator ckt but i am not able to recieve anything from the memory device, i have worked with a 5v slave device my code is working fine. but showing problem with this 2.7v device

 

[rajeshbij]

"... m already using vtg divider ckt for SCK, CS and SI pin, but problem M facing is for SO pin..."
There's no need to convert the voltage level for SO pin as the uC (5V) can read the logic signals at 2.7v level . We only need to lower the voltage levels from 5v to 2.7v just to protect the SD card or other slave device.
Hope its clear now.