The ’HC74 contain two independent D-type
positive-edge-triggered flip-flops. A low level at
the preset (PRE) or clear (CLR) inputs sets or
resets the outputs regardless of the levels of the
other inputs. When PRE and CLR are inactive
(high), data at the data (D) input meeting the setup
time requirements are transferred to the outputs
on the positive-going edge of the clock (CLK)
pulse. Clock triggering occurs at a voltage level
and is not directly related to the rise time of CLK.
Following the hold-time interval, data at the
D input can be changed without affecting the
levels at the outputs.
The SN54HC74 is characterized for operation
over the full military temperature range –55°C to
125°C. The SN74HC74 is characterized for
operation from –40°C to 85°C.