Makefile produces build/debug file via ca65/ld65.
WIP: SD card support.
WIP: SD card support.
sd: pin mapping updated.
sd: deselect chip during init (SS=HIGH).
sd: private csHigh / csLow moved down in source code.
sd: SpiByte loop comparison simpler (DEY, not INY+CPY).
sd: sdCardCommandZeroArg sets CMD upper bits correctly.
sd: WIP; send CMD0, CMD55, ACMD41. Wait for responses.