Pointer to msg buffer
Pointer to the function-supplied message
area.
The assembler always sets this pointer before invoking an external function. The external function can put up to 255 bytes of message text into the area addressed by this field.
Pointer to the function-supplied message
area.
The assembler always sets this pointer before invoking an external function. The external function can put up to 255 bytes of message text into the area addressed by this field.