590 CHAPTER 12 / MODULE AND BIT-SLICE DEVICES
12.4 SHIFT-REGISTER COUNTERS
Shift registers are normally designed to be operated in one or more of the noncyclic “data”
modes of operation given at the beginning of Section 12.2. However, the flip-flops of a regis-
ter can be configured to operate in a “nondata” cyclic fashion with or without external logic
depending on the desired effect. Registers that are configured to operate in a cyclic fashion
are called shift-register counters. These counters cycle through a sequence of states that gen-
erally conform to one or three types of codes: 1-hot code (Table 2.11), creeping code (Table
2.10), and a pseudo-random code. For future reference, the names of these counters are
Ring counters
Twisted ring (Johnson) ...