MM54HC166/MM74HC166
8-Bit Parallel In/Serial Out Shift Registers
General Description
The MM54HC166/MM74HC166 high speed 8-BIT PARALLEL-
IN/SERIAL-OUT SHIFT REGISTER utilizes advanced
silicon-gate CMOS technology. It has low power consumption
and high noise immunity of standard CMOS integrated
circuits, along with the ability to drive 10 LS-TTL loads.
These Parallel-In or Serial-In, Serial-Out shift registers feature
gated CLOCK inputs and an overriding CLEAR input.
The load mode is established by the SHIFT/LOAD input.
When high, this input enables the SERIAL INPUT and couples
the eight flip-flops for serial shifting with each clock
pulse. When low, the PARALLEL INPUTS are enabled and
synchronous loading occurs on the next clock pulse. During
parallel loading, serial data flow is inhibited. Clocking is accomplished
on the low-to-high level edge of the CLOCK
pulse through a 2-input NOR gate, permitting one input to
be used as a clock enable or CLOCK INHIBIT function.
Holding either of the clock inputs high inhibits clocking;
holding either low enables the other clock input. This allows
the system clock to be free running, and the register can be
stopped on command with the other clock input. The
CLOCK INHIBIT input should be changed to the high level
only while the clock input is high. A direct CLEAR input overrides
all other inputs, including the CLOCK, and sets all flipflops
to zero.
The 54HC/74HC logic family is functionally as well as pin
out compatible with the standard 54LS/74LS logic family.
All inputs are protected from damage due to static discharge
by internal diode clamps to VCC and Ground.