# What's the difference between ATMega1284 and ATMega1284p?

I want to buy an Atmega1284p, doing a research on my local hardware seller (RS), I've found two models, the Atmega1284p-pu and the Atmega1284-pu. Reading the specs I don't see any difference (maybe I am missing something).

The only thing I saw is that Atmega1284-pu has the window to clear the memory using UV light. I really want to understand the difference, because one of them is cheaper and this will affect my criteria.

The p stands for picoPower. It uses less power than the normal chip.

Atmel picoPower devices can operate down to 1.62V while still maintaining all functionality, including analog functions. They have short wake-up time, with multiple wake-up sources and multiple sleep modes.

only thing I saw was a difference in hardware, the Atmega1284-pu have the window that allow to clear the memory using UV light.

I don't believe this is correct, although from the link you provided it does look that way. I think that company just uses that picture as a default picture, not an actual picture of the device.

There are a couple other options that Atmel uses when labeling their chips, you can read more about it in my post here.

The letter before the dash (-) is the Option Designator and means:

• P   "Picopower" low-power parts
• A   Newer Fabrication process, lower voltage, lower power, non-Atmel fabricated parts with possibly more noise on A/D inputs
• V   Low-voltage, lower clock frequency parts before "A" came along
• and nothing is the default part
• And the UV window? why it makes the micro cheaper? Jan 4, 2013 at 9:57
• @DomingoSL to the best of my knowledge there is no UV window. I think the site you linked just uses that as a default picture. Jan 4, 2013 at 10:02
• Very good answer thank you!, still, i have a doubt, why the part with the "p" is the cheaper one? Low-power parts aren't the more expensive than the normal one? Jan 4, 2013 at 14:47
• @DomingoSL It has a lot more to do with how many that distributor ordered, price and demand. For example at mouser (they don't stock both the 1284 and 1284p, so I used the 168) the atmega168 is more than a dollar cheaper then the atmega168p. These prices will fluctuate, but it probably has more to do with demand and quantity. Jan 5, 2013 at 13:49

I can't post comments yet so this is not a answer to the question, but i just checked the datasheet and there at the end are about 20-30 pages for every model with characteristics. 1284 and 1284p have their own pages and plots, apart from model suffix and figures number there is not a single different bit anywhere i looked. Manually compared the datasheets and nowhere is mentioned about difference. Power supply voltages are identical everywhere and consumption and so on.
Is it possible that they simply didn't put correct information there, and just copy 1284 data?

• The main difference in the pico power units is that you have the ability to turn off more of the peripheral modules. So the end device uses less power. Jan 4, 2013 at 10:31
• I believe you are right, just can't find it anywhere. Can you point me to some source? If ATMEL make the effort to put a difference between models table, this should be there, but this is not the case.
– zzz
Jan 4, 2013 at 10:35
• Look at section 35.4 atmel.com/Images/doc8272.pdf it mentions that the non-pico devices were added. Other than that I can't find much. Jan 4, 2013 at 10:39
• Looks like very poor job from ATMEL in this case. Still I learn something new, so I will call it a day. :)
– zzz
Jan 4, 2013 at 11:29