Alan, Maybe I didn't explain clearly. In page mode the EEPROM only takes 64 bytes and doesn't write it just buffers it right after stop condition showed up It will spend it's own time to write it. Since it does it by itself we do not see how long it takes. Make it short there is no fast write this is just a work around or another method of writing that will free up CPU time in background. I just tested: right after page right the pic will turns off the EEPROM Power the EEPROM only stored a few bytes. I am not too far to find out how long inside external EEPROM takes to write all 64 bytes of data. The reason I am turning it off because of I need to write data after power Disconnection and this is USB device and I only have 10ms time to write 64 bytes. Thanks Andre -----Original Message----- From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of Alan B. Pearce Sent: Thursday, September 25, 2008 2:01 AM To: Microcontroller discussion list - Public. Subject: Re: [pic:] I2C EEPROM write speed ? >According to 24lc256 datasheet EEPROM itself only stores the >64 byte of data In temporary storage I am assuming in RAM then >after the master generates Stop condition then eeprom itself >will write all 64 bytes of data. Right, now you are learning. The next trick is that those 64 bytes of data get written in the same time as a single byte, i.e. the 6.5mS that you have been seeing. So by writing your 32kB code in 64 bit chunks instead of a byte at a time, you will speed the write time by 64 times, so your 270 seconds (4.5 minutes) comes down to 4.2 seconds for 32kB!!! -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist IMPORTANT NOTICE: This notice constitutes Proprietary Rights identification of this email including all attachments, which is property that is intended only for the use of the individual or entity to which it is addressed. It also may contain proprietary data or information that is privileged, confidential, or otherwise protected from disclosure under applicable law. The recipient of this data agrees to abide by the United States Export Control of Technical Data and Equipment under the International Traffic in Arms Regulations (ITAR) and Export Administration Regulations (EAR). The recipient agrees to abide by these laws and their regulations not only for export and re-export, but for disclosure to non-U.S. citizens. This email does not grant or assign rights of ownership in the proprietary subject matter herein, nor shall it be construed as a joint venture, partnership, teaming agreement, or other formal business relationship. If the reader of this e-mail transmission! is not the intended recipient or the employee or agent responsible for delivering the transmission to the intended recipient, you are hereby notified that any dissemination, distribution, copying or use of this e-mail or its contents is strictly prohibited. Please notify the sender you received it in error by responding to the e-mail and then permanently delete it and all copies of the e-mail immediately, including any copies of it in your deleted email folder. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist