05-10-2012, 07:07 PM
I'm assuming that you're going for a RAM-based solution for the SD cart, and not in-device flash programming?
You'd need to decide what kind of SD interface you plan to use. Something bare bones where the host CPU has to do all the work, or something that comes integrated with a uC or CPLD for hardware assisted communication with the SD card? This choise determines a few other things. For example, you don't want to access the SD card in SPI mode on a slow host CPU as that would kill the performance completely. OTOH, if you had some dedicated hardware to take care of that then SPI mode would be preferable over native mode as it would simplify the code a bit.
You'll also want to consider how you're going to map the SD interface and the cart RAM into the TLCS900 memory space. With a 32-bit address space this shouldn't be a big issue, but it's still something to think about.
Only after all that has been decided is it worth beginning to do any software design.
For PFF you really want a C compiler, which could become a problem since I don't know of any C compilers that target the TLCS900H. Is Toshiba's compiler still downloadable from somewhere?
The lower-level disk I/O code that initialises the card and reads sector data is not such a big deal and can be written without too much effort once the SD interface and memory mapping is known. Here's the Z80 implementation I made for the neoflash sega master system cart: http://code.google.com/p/neo-myth-menu/s...skio_asm.s
You'd need to decide what kind of SD interface you plan to use. Something bare bones where the host CPU has to do all the work, or something that comes integrated with a uC or CPLD for hardware assisted communication with the SD card? This choise determines a few other things. For example, you don't want to access the SD card in SPI mode on a slow host CPU as that would kill the performance completely. OTOH, if you had some dedicated hardware to take care of that then SPI mode would be preferable over native mode as it would simplify the code a bit.
You'll also want to consider how you're going to map the SD interface and the cart RAM into the TLCS900 memory space. With a 32-bit address space this shouldn't be a big issue, but it's still something to think about.
Only after all that has been decided is it worth beginning to do any software design.
For PFF you really want a C compiler, which could become a problem since I don't know of any C compilers that target the TLCS900H. Is Toshiba's compiler still downloadable from somewhere?
The lower-level disk I/O code that initialises the card and reads sector data is not such a big deal and can be written without too much effort once the SD interface and memory mapping is known. Here's the Z80 implementation I made for the neoflash sega master system cart: http://code.google.com/p/neo-myth-menu/s...skio_asm.s