flip-flop与latch的区别

flip-flop 与latch的区别
《数字设计--原理和实践》(John )书中的定义：
All digital designers use the name flip-flop for a sequential device that noramlly samples its inputs and changes its outputs only at times determined by a clocking signal. On the other hand, most digital designers use the name latch for a sequential device that watches all of its inputs continuously and changes its outputs at any time, independent of a clocking signal. Some text books and digital designers may (incorrectly) use the name “flip-flop” for a device that we call a “latch”.
结论
-- 寄存器（register)：一般是指边沿触发的触发器，概念有点模糊。

-- 锁存器（latch)：电平触发。

-- 触发器（flip-flop)：边沿触发
-- 在fpga中一般避免用latch，因为在FPGA中触发器资源丰富，不用白不用，latch由于是电平触发的，相对触发器来说容易产生毛刺，电路不稳定。

latch的优点是完成同一个功能所需要的门较
触发器要少，所以在asic中用的较多。

关于flip-flop，网上辞典的解释：
（1）An electronic circuit that alternates between two states. When current is applied, it changes to its opposite state (0 to 1 or 1 to 0). Made of several transistors, it is used in the design of static memories and hardware registers.
（2）A digital logic circuit that can be in one of two states which it switches (or “toggles”) between under control of its inputs. It can thus be considered as a one bit memory. Three types of flip-flop are common: the SR flip-flop, the JK flip-flop and the D-type flip-flop (or latch).
Early literature refers to the “Eccles-Jordan circuit” and the “Eccles-Jordan binary counter”, using two vacuum tubes as the active (amplifying) elements for each bit of information storage. Later implementations using bipolar transistors could operate at up to 20 million state transitions per second as early as 1963.。