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Rabbit 4000 Designer’s Handbook rabbit.com 51

The aspect non-terminal represents an individual aspect of an origin. This non-terminal may be one of

three things. It may be the "size" terminal, in which case the compiler assigns the size of the origin in bytes

to the macro. It may be the "fragments" terminal, wherein the compiler will assign the number of frag-

ments within the origin to the macro. Lastly, it may be the non-terminal quality followed by position as

explained below.

This non-terminal specifies a quality of a particular boundary, and may be any of the terminal symbols

"physical", "logical", or "segment". Each correspond to the physical address, logical address, and segment

value respectively of the origin boundary in context. If the origin is not a logical origin, then the segment

and logical terminals will represent the physical boundary converted to an xxx:Exxx address type.

The position non-terminal is either "start" or "end", and represents the beginning or end respectively of the

origin in context.

6.5.2 Origins Prior to Dynamic C 10.21

The following grammar (in BNF) describes the syntax used for the declaration of origin statements prior to

Dynamic C version 10.21.

origin-directive : #origin-type identifier origin-designator

origin-designator : action-expression | origin-declaration

origin-declaration : physical-address size [follow-qualifier][I&D-qualifier][action-qualifier]

[debug-qualifier]

follow-qualifier : follows identifier [splitbin]

I&D-qualifier : ispace | dspace

action-qualifier : resume | apply

size : constant-expression

physical-address : constant-expression constant-expression

The non-terminals, identifier and constant-expression, are defined in the ANSI C specification. Basically,

an identifier is a sequence of letters and digits that must start with a letter. The underscore character is

considered a letter. The definition of constant-expression is more involved as it winds up the restricted

subset of operators that are allowed in the evaluation of the expression, but the result is a constant. For a

comphrensive definition of the non-terminals, identifier and constant-expression, please refer to

Appendix A in “The C Programming Language” by Kernighan and Ritchie.

6.5.2.1 Origin Directive Semantics

An origin directive associates a code pointer and a memory region with a particular type of code. The type

of code is specified by #origin-type.