My new to me 68hc11 board is waiting at the post office! It's a much wanted (I don't NEED it mind you) replacement for the one that was damage in a fire. For under $15 off of ebay shipped, that's a bargain if it works! I'm guessing this is based off of the Buffalo monitor ROM.
Expect a 68hc11 version of Microsoft like BASIC in the future (yet another project to divide my time further) There aren't going to be a lot of changes to the main interpreter. Memory moves won't need to use the stack pointer, I can dedicate the Y register to pointing to the next character for large sections of the interpreter. I/O would have to completely change though. The bit banger cassette I/O will probably be replaced with an IDE port and simple DOS. Video out and keyboard will be through a terminal (Buffalo calls?). I may decide to stick on a V9958 and PC keyboard interface.
The hc11 has a few added instructions that may come in handy. The hc11 supports XGDX like the 6803 and XGDY which might allow the use of X and Y for temporary storage without having to use direct page RAM in a few places. It's only a space saving optimization if I'm storing 8 bit registers in X as it takes 3 clock cycles and using Y requires 4. It would be faster or the same speed to save D in X though. Y requires 2 byte opcodes, so it's slower than X and slower than using the stack pointer.but you don't have to disable interrupts like with the stack pointer. It's definitely faster than constantly changing X.
There is a version of GCC for the 68hc11, so that's a definite improvement over the 6803.
Expect a 68hc11 version of Microsoft like BASIC in the future (yet another project to divide my time further) There aren't going to be a lot of changes to the main interpreter. Memory moves won't need to use the stack pointer, I can dedicate the Y register to pointing to the next character for large sections of the interpreter. I/O would have to completely change though. The bit banger cassette I/O will probably be replaced with an IDE port and simple DOS. Video out and keyboard will be through a terminal (Buffalo calls?). I may decide to stick on a V9958 and PC keyboard interface.
The hc11 has a few added instructions that may come in handy. The hc11 supports XGDX like the 6803 and XGDY which might allow the use of X and Y for temporary storage without having to use direct page RAM in a few places. It's only a space saving optimization if I'm storing 8 bit registers in X as it takes 3 clock cycles and using Y requires 4. It would be faster or the same speed to save D in X though. Y requires 2 byte opcodes, so it's slower than X and slower than using the stack pointer.but you don't have to disable interrupts like with the stack pointer. It's definitely faster than constantly changing X.
There is a version of GCC for the 68hc11, so that's a definite improvement over the 6803.
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