You can refer to a general register using the AND, OR, assignment-of-value, COPY, or LIST subcommands by specifying a decimal integer followed by an R. The decimal integer indicates the number of the register and must be in the range 0 through 15. Other references to the general registers imply indirect addressing.

If your program issues the STIMER macro or involves asynchronous interruptions, the contents of your registers may be changed by interruptions even though you are in subcommand mode and your program does not get control.