The Chip
Here is a picture of the SX microcontroller ICs.
As you can see there are a couple different types of chips and packages. There are four different ICs total in the SX microcontroller family. There use to be a couple more, but that is a different story. In the picture you can see an SX28AC/DP-G which is the tallest and longest IC. This IC is a through-hole dual inline pin package (a.k.a. DIP). The SX28 has 20 I/O pins. The other three chips are in SMT packages. The one on the left with pins around the whole package is an SX48BD-G and is the biggest SX chip produced with 36 I/O pins. The blurry chip at the bottom of the picture is an SX20AC/SS-G and has 12 I/O pins. The remaining chip on the right is an SX28AC/SS-G. This IC is just like the DIP IC, but in a surface mount design.
As you may be able to tell from the naming scheme and picture, the SX48 has 48 pins, the SX28 has 28 pins and so on. The “-G” denotes that the IC is lead free or RoHS compliant. The DP/SS/BD is an abbreviation for the type of package the IC is such as DIP, SSOP and PQFP. If what I said is confusing, you can find the same information in the data sheet for the ICs on Parallax’s web site.
Here is another photo of the ICs, though not as good. I turned the flash on so you could see the labeling on the IC.
July 11th, 2008 at 9:51 pm
For a hobbiest, isn’t the SX28AC/DP-G the best choice? I am not a surface mount solderer and not sure I want to be with 50 year old eyes ;-). I am also not making a mass produced product where I might include one of the other types more easily. Are they functionally the same?
How does the SX Key allow program of the surface mount IC’s? My understanding of this is limited.
I will download the data sheets and have a look! Thanks again.
July 12th, 2008 at 8:12 am
There are different hobbyists with different needs. For me, I don’t mind the surface mount chips because they save board space. For other, I can see the advantages to the DIP style package. There are pros and cons in each category. Like you said, the surface mount versions may be hard to solder, but with a little practice that can be done too.
The SX20 and SX28 (and their IC package variants) are very similar. The main difference is the quantity of I/O pins. The SX48 is slightly different because there is additional memory and registers. I am still reading on this, but will certainly have a post about it in the future.
As far as programming goes the SX-Key is used to program any of the variants. usually a four pin, 0.1″ space header is provided for in a design. The SX-Key attaches to this header to download and to debug the chip that is in the system. Another option would be to “burn” the program to your chip before installing. This is only recommended once you have created and proven your program. If you are using the DIP chip, then the program can be burned using a SX Tech Demo Board since it has a socket for the DIP chip. The other chips you would have to obtain a socket and fashion it to the demo board or hire a commercial programmer (for large product runs).
July 13th, 2008 at 2:38 am
Thanks for the great answer. I think I am starting to get a little handle on how this all works.