Explicit address

An explicit address is specified by coding two absolute expressions as follows:

The first is an absolute expression for the displacement, whose value must lie in the range 0 through 4095 (4095 is the maximum value that can be represented by the 12 binary bits available for the displacement in the object code), or in the range -524,288 to 524,287 for long-displacement instructions.
The second (enclosed in parentheses) is an absolute expression for the base register, whose value must lie in the range 0 through 15.

An explicit base register designation must not accompany an implicit address. However, in RX-format instructions, an index register can be coded with an implicit address as well as with an explicit address. When two addresses are required, each address can be coded as an explicit address or as an implicit address.