Two quick remarks: >> 2. how the data from data stack (or from return stack) are passed to >> assembler
- data stack (all elements EXCEPT top of the stack) are kept close to the end of RAM (end of RAM - 128), growing down. - TOP of the stack is kept in register pair (tosh:tosl) >> 3. how the data are passed from asm. back to data stack or return >> stack - if you just change top of the stack (say remove 1 parameter and put 1 cell of results) just change contents of tosh:tosl registers - "loadtos" macro fetches the second item on stack and loads it into the tosh:tosl, while moving stack pointer down - - so it effectively the same as DROP. Of course, if one needs to preserve top of stack another "ld" command can be used to load 2nd, 3rd, etc. elements into other registers. - "storetos" macro stores the TOS on to the stack, therefore it is how DUP is implemented. If you want just to push something on stack just "storetos" and modify tosh:tosl. - return stack is the machine stack. it starts at the end of RAM and grows downward (toward smaller addresses), the same direction as the data stack. It means you have 128 bytes (64 16-bit words) for the return stack available by default. - second item on a data stack is pointed by the YH:YL register pair - push, pop operate on the return stack then (see >r, r>, r@) - inner interpreter stores current Forth instruction pointer in the register pair XH:XL and pushes it/pops off the return stack as necessary. It's all in amforth.asm - first 87 lines --Marcin ------------------------------------------------------------------------------ Automate Storage Tiering Simply Optimize IT performance and efficiency through flexible, powerful, automated storage tiering capabilities. View this brief to learn how you can reduce costs and improve performance. http://p.sf.net/sfu/dell-sfdev2dev _______________________________________________ Amforth-devel mailing list Amforth-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/amforth-devel
