Choice of Eight Latches or Eight D-Type

Flip-Flops in a Single Package

3-State Bus-Driving Outputs

Full Parallel Access for Loading

Buffered Control Inputs

Clock-Enable Input Has Hysteresis to

Improve Noise Rejection (’S373 and ’S374)

P-N-P Inputs Reduce DC Loading on Data

Lines (’S373 and ’S374)

description

These 8-bit registers feature 3-state outputs

designed specifically for driving highly capacitive

or relatively low-impedance loads. The

high-impedance 3-state and increased

high-logic-level drive provide these registers with

the capability of being connected directly to and

driving the bus lines in a bus-organized system

without need for interface or pullup components.

These devices are particularly attractive for

implementing buffer registers, I/O ports,

bidirectional bus drivers, and working registers.

The eight latches of the ’LS373 and ’S373 are

transparent D-type latches, meaning that while

the enable (C or CLK) input is high, the Q outputs

follow the data (D) inputs. When C or CLK is taken

low, the output is latched at the level of the data

that was set up.

The eight flip-flops of the ’LS374 and ’S374 are

edge-triggered D-type flip-flops. On the positive

transition of the clock, the Q outputs are set to the

logic states that were set up at the D inputs.

Schmitt-trigger buffered inputs at the enable/clock lines of the ’S373 and ’S374 devices simplify system design

as ac and dc noise rejection is improved by typically 400 mV due to the input hysteresis. A buffered

output-control (OC) input can be used to place the eight outputs in either a normal logic state (high or low logic

levels) or the high-impedance state. In the high-impedance state, the outputs neither load nor drive the bus lines

significantly.

OC does not affect the internal operation of the latches or flip-flops. That is, the old data can be retained or new

data can be entered, even while the outputs are off.