2 Nov
2013
2 Nov
'13
5:31 p.m.
On 11/02/2013 05:03 PM, Alan Hightower wrote:
Why don't you guys just run the MFM signal through a shift in and
shift out register. Then you could read the input and write output
data at a byte wide port level. Would cut the interrupt rate way
down and let you use a lesser MCU.
What do you think ISP is? Just a shift register. The PIC32 even has
32-bit wide DMA from its SPI ports and lots of fast SRAM
onboard--128K-192K isn't unsual. Other than your non-volatile (e.g.
SDHC card) memory interface and the ST506 signal (differential and TTL),
an emulator should be pretty small in terms of real-estate. Many PIC32s
also have 5V-tolerant inputs.
Nowadays, there's not a lot of payoff in adding external logic to enable
use of a lesser MCU. I did a floppy emulator design using an AVR
ATMega, external SRAM and miscellaneous glue and the price for the BOM
came to *more* than a simple low-end ARM. Silicon is cheap.
--Chuck