On a sunny day (Thu, 21 Jun 2007 14:45:41 -0000) it happened Antti wrote in :
Hide quoted text -
From:
------------------------------------------------------------ Technical explanation
SD supports at least three transfer modes:
- One-bit SD mode (separate command and data channels and a proprietary transfer format) * Four-bit SD mode (uses extra pins plus some reassigned pins) * SPI mode (basically, a simpler subset of the SD protocol for use with microcontrollers)
All memory cards must support all three modes, except for microSD where SPI is optional. The cards must also support clock frequencies of up to 25 MHz for regular cards, and 50 MHz for high-speed cards.
Royalties for SD/SDIO licenses are imposed for manufacture and sale of memory cards and host adapters ($1000 per year plus membership at $1500/year) but SDIO cards can be made without royalties and MMC host adapters do not require a royalty.
-------------------------------------------------------------
So, I dunno. SD 2500$ /year for an adapter, how many cards will you sell? 10? Do I see this right?
8 SD or MMC cards of 1GB is now about 64 Euro I think. 10 Euro for the rest of the parts. 250 for the license??????? Not counting other IP you will need.You tell me.
I think if cards from the same batch are used the timing issue is not that different. But you are right, you'd need to monitor for CRC or whatever, and wait for all 8 cards to complete. But the same issue applies for any other system, even or even more so if you want to 'stagger' the cards as in this example, maybe that is why so much logic? Maybe the guy who designed that board ran into this.