FEATURES
•Gated input enable for hold (do nothing) mode
•Gated output enable control
•Edge-triggered D-type register
•Asynchronous master reset
•Output capability: bus driver
•ICC category: MSI
GENERAL DESCRIPTION
The 74HC/HCT173 are high-speed Si-gate CMOS devices
and are pin compatible with low power Schottky TTL
(LSTTL). They are specified in compliance with JEDEC
standard no. 7A.
The 74HC/HCT173 are 4-bit parallel load registers with
clock enable control, 3-state buffered outputs (Q0 to Q3)
and master reset (MR).
When the two data enable inputs (E1 and E2) are LOW, the
data on the Dn inputs is loaded into the register
synchronously with the LOW-to-HIGH clock (CP)
transition. When one or both En inputs are HIGH one
set-up time prior to the LOW-to-HIGH clock transition, the
register will retain the previous data. Data inputs and clock
enable inputs are fully edge-triggered and must be stable
only one set-up time prior to the LOW-to-HIGH clock
transition.
The master reset input (MR) is an active HIGH
asynchronous input. When MR is HIGH, all four flip-flops
are reset (cleared) independently of any other input
condition.
The 3-state output buffers are controlled by a 2-input NOR
gate. When both output enable inputs (OE1 and OE2) are
LOW, the data in the register is presented to the Qn
outputs. When one or both OEn inputs are HIGH, the
outputs are forced to a high impedance OFF-state. The
3-state output buffers are completely independent of the
register operation; the OEn transition does not affect the
clock and reset operations.
QUICK REFERENCE DATA
GND = 0 V; Tamb = 25 C; tr = tf = 6 ns
Notes
1. CPD is used to determine the dynamic power dissipation (PD in W):
PD = CPD VCC
2 fi (CL VCC
2 fo) where:
fi = input frequency in MHz
fo = output frequency in MHz
(CL VCC
2 fo) = sum of outputs
CL = output load capacitance in pF
VCC = supply voltage in V
2. For HC the condition is VI = GND to VCC
For HCT the condition is VI = GND to VCC 1.5 V
ORDERING INFORMATION