Flash Interface with AT91RM9200

The VPEN pin is used to lock/unlock the device globally for writing. If you wish to have some certainty that the device may not be written to in a spurious manner (during startup/shutdown, for example), connect this pin (with a pulldown of about 100k) to an IO port bit. The pulldown will ensure VPEN is invalid until the processor starts up and initialises the port bit, preventing spurious writes. If you believe there should be no problem, pull the line to Vdd through 100k. This will make the device unlocked (at that level, anyway) at all times. Note you still have to write to the device to unlock blocks.

The USB spec can clear this up. An upstream (slave) port has to signal it is present. It does this by pulling the DP line high through 1.5k,

1%. Releasing this line permits the downstream (host) to pull *both* lines low (through 15k). With both lines low, no active device is assumed to be attached.

Cheers

PeteS

use

Hi Thanks for the suggestion. If we are using a single flash memory IC, i it possible to have a glueless connection? in that case, can we connec the chip select signal from controller directly to CE0 (with CE1 and CE connected to GND)? Regards, S Mahesh.