The 'F407 Data Access Register (DAR) performs memory address arithmetic for RAM resident stack applications It contains three 4-bit registers intended for Program Counter (R0) Stack Pointer (R1) and Operand Address (R2) The 'F407 implements 16 instructions which allow either pre- or post-decrement increment and register-to-register transfer in a single clock cycle It is expandable in 4-bit increments and can operate at a 30 MHz microinstruction rate on a 16-bit word The TRI-STATE outputs are provided for busoriented applications The 'F407 is fully compatible with all TTL families