We can think of the difference between built-in firmware andequivalent hardware as a minor implementation detail, provided that weare sure in either case that it won't be changed. A hardware circuitcan't be changed; that's its nature. If it's acceptable for a deviceto be implemented with internal circuitry that no one can alter, thenan internal program that no one can alter is no worse. It would notbe sensible to reject an equivalent internal software implementation,when operationally they are indistinguishable.