What is the difference between the device identification register (IDR) value and the device revision markings on Maxim devices?
A6. The device revision, printed on the top of the package, consists of an alphanumeric combination that is two characters in length. The alpha character denotes the current level of an all-layer die revision, with the first die being denoted with the letter ‘A’. The numeric character denotes the current level of a metal layer die revision, with the first die being denoted with the number ‘1’. If only the metal layers of the die are revised, then the numeric portion is increased by one. When all the layers of the die are revised, then the alpha portion is increased by one letter and the numeric portion is returned to the number ‘1’. Further changes follow the same standard. For all Maxim T1/E1 devices with an 8-bit data bus, the device identification register (IDR) is eight bits in length. The upper four bits are used to identify the device family (e.g., the DS2155, DS21354, DS21552, etc.) The lower four bits are used to identify the specific revision of the die. Because the lower four
