Editing Microsequencer (section)

==Simple example==
The [http://www.bitsavers.org/pdf/digitalScientific/ Digital Scientific Corp.] Meta 4 Series 16 computer system was a user-microprogrammable system first available in 1970. Branches in the microcode sequence occur in
one of three ways.<ref>{{cite book|url=http://www.bitsavers.org/pdf/digitalScientific/7032MO_Meta4Series16RefMan.pdf|title=Digital Scientific Meta 4 Series 16 Computer System Reference Manual|id=7032MO|publisher=Digital Scientific Corporation|date=May 1971}}</ref>    
* A [[Branch (computer science)|branch]] microinstruction specifies the address of the next instruction, either conditionally or unconditionally. The logical index (IX) option causes the 16-bit Link register to be [[Logical disjunction|logical ORed]] into the branch address, thus providing a simple indexed branch capability.

* All the arithmetic/logical instructions allow the jump (J) modifier, which redirects execution to the microinstruction addressed by the Link register.

* All the arithmetic/logical instructions allow both the decrement counter (D) and jump (J) modifiers. In this case, the 8-bit loop counter register is decremented. If it is then not zero, a branch is taken to the contents of the Link register. If it is zero, execution continues with the next instruction.

One more sequencing option allowed on a branch instruction is the execute (XQ) option. When specified, the single instruction at the branch address is executed, but then execution continues after the original branch instruction. The IX option can be used with the XQ option.