I traced the issue with a function called my_args_copy(). That led me to a forth word called my-args. I'm not sure what this word does, or where it is defined.
my-args ( -- arg-str arg-len ) F 0x202 Return the instance-argument string for this instance.
Return the instance-argument string that was passed to the current instance (when the current instance was created).
set-args ( arg-str arg-len unit-str unit-len -- ) F 0x23F
Set address and arguments of new device node.
unit-string is a text string representation of a physical address within the address space of the parent device. Translate unit-string to the equivalent numerical representation by executing the parent instance’s “decode-unit” method. Set the current instance’ s probe-address (i.e., the values returned by my-address and my-space) to that numerical representation.
Copy the string arg-string to instance-specific storage, and arrange for my-args to return the address and length of that copy when executed from the current instance.
NOTE—set-args is typically used just after new-device. new-device creates and selects a new device node, and set-args sets its probe-address and arguments. Subsequently, the device node’s properties and methods are created by interpreting an FCode program with byte-load or by interpreting Forth source code.
NOTE—The empty string (any string of zero length) is commonly used as the arguments for a new device node, for example: 0 0 " 3,2000" set-args