"Dresner, Norman A." wrote:
>
> Let me try to clarify the situation a little.
> to use the segment that the 80188 sees that data at. In this
> example we need to take 0x000D3478 and transform it into 0x1000:3478.
#define DPM_OFFSET 0xC000
register int segment,cpu_address,device_address;
segment = (cpu_address & 0xFFFF0000 - DPM_OFFSET) << 16;
device_address = cpu_address & 0x0000FFFF + segment;
segment = device_address >> 16 + DPM_OFFSET;
cpu_address = device_address & 0x0000FFFF + segment;
Although this looks complicated in C it gets translated into some really
fast asm. It uses some of the fastest asm instructions:
shift,
bitwise-and ( bit masking),
add,
subtract.
- Kal.
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