EEyE:
ElEctriEyE wrote:
1) The Micron FLASH IC I posted about a few posts ago was listed on DigiKey as a 256Mbx4 (1Gbit). Does the x4 refer to it's capability to have quad I/O? and not it's internal storage arrangement? And...
I am pretty sure that Digikey has defined the part incorrectly. Internally it is going to be 8-bit cells in pages, sectors, and blocks as you'd expect. The each has a part and manufacturer ID that provides specifics about the internal organization if that makes a difference for the user. Most of these parts conform to a JEDEC serial Flash memory interface. Some may have some custom/proprietary commands, but most respond to a common set of commands. Many of those commands are common from the smallest parts to the largest parts. Most of the newer parts support x1, x2, and x4 read/write ports. All parts start off in the x1 configuration, and the user can command them to switch into the x2 or x4 I/O configuration.
Another common interface configuration issue is the selection of 24-bit (3 bytes) and 32-bit (4 bytes) addressing. Any device greater than 128Mb (16MB) will require more that 3 bytes of address, but those additional bits can be supplied in several ways. We have just opted to use the larger 4 byte address mode rather than using the 3 byte address mode plus explicit management of the other bits.
When supporting the x2 and x4 I/O configuration, some of the pin functions, e.g. nHOLD, are no longer available; I doubt that you'd be particularly interested in that feature.
ElEctricEye wrote:
Is it safe to assume when using just regular SPI or extended SPI that 8 bits are shifted out for an LSB and another 8 bits for the MSB? It's tough to read these data sheets.
My eyes rolled back in my head too when I first looked at the datasheet of one of these larger SPI Flash devices.
The nice thing is that the interface is very standard, and with some careful attention to the part ID, it's possible for a single driver to support a number of devices and vendors. We just choose parts that have a common page and sector size such 512 words per page and 4KB per sector. Luckily, there are a wide number of devices from several vendors that provide these features.