Branch instructions have a 6-bit opcode field, a 5-bit Ra field and a 21-bit displacement field. The Ra field specifies a register to be tested by a conditional branch instruction, and if the condition is met, the program counter is updated by adding the contents of the displacement field with the program counter. The displacement field contains a signed integer and if the value of the integer is positive, if the branch is taken then the program counter is incremented. If the value of the integer is negative, then program counter is decremented if the branch is taken. The range of a branch thus is ±1 Mi instructions, or ±4 MiB. The Alpha Architecture was designed with a large range as part of the architecture's forward-looking goal.
Despite all of the background technology, Alpha-Beta filtering boils down to a simple set of equations easily packaged as the ENGSPEED processing command that you can use with your Data Acquisition Processor ( DAP ) board system. Updated speed estimates are available within milliseconds of the arrival of each timing pulse. Interpolated speed estimates are available at all times between. Accurate estimates, fast response, and reliability of DAP operation, in addition to the data capture and logging processes supported simultaneously, make the ENGSPEED command a useful tool for engine speed monitoring and control applications.