idea new200911

 

ON 20091109@11:49:00 AM at page:
On a web page you were interested in at:
http://techref.massmind.org/techref/idea/minimalcontroller.htm#40126.4923611111
James Newton[JMN-EFP-786] Says

If the "a" register has been initialized to point to the beginning of a sub thread of bytecode in the EEPROM, and we write "a(b)" the "(" could set a flag, indicating that a subroutine call was being parameterized, then the following byte codes could be loaded into a special parameter call stack as references to the actual memory addresses. The ")" would then push the return address (the current PC), a count of parameters, and load the value of the a register into PC. 
<P>
In the sub thread, references to "a", "b", "c", etc... would point to the values of the parameters on the stack, instead of to the regular memory location for those registers. E.g. in the "a" routine, a reference to "a" would actually end up affecting the value of "b" since the call was started with "a(b)". If the call to "a" had been made with "a(c)" then a reference to "a" would affect "c".
<P>
At the end of the sub thread, the PC would be popped from the stack and the parameter pointers cleared.
<P>
This mixing of letters as registers and as pointers to subroutines is less than ideal, but perhaps better than limiting the number of subroutines that are possible.

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