M74HCT651 Datasheet, PDF (3/12 Pages) STMicroelectronics – HCT651 OCTAL BUS TRANSCEIVER/REGISTER 3-STATE, INV. HCT652 OCTAL BUS TRANSCEIVER/REGISTER 3-STATE

M74HCT651/652
TRUTH TABLE
HCT652 (The truth table for HCT651 is the same as this, but with the outputs inverted)
GAB GBA CAB CBA SAB SBA
XXXX
LH
XX
A
INPUTS
Z
INPUTS
B
INPUTS
Z
INPUTS
OUTPUTS INPUTS
X* X X L
L
L
H
H
X*
XL
L
L
LL
H
H
FUNCTION
Both the A bus and the B bus are inputs
The output functions of the A and B bus are disabled
Both the A and B bus are used for inputs to the
internal flip-flops. Data at the bus will be stored on
low to high transition of the clock inputs
The A bus are outputs and the B bus are inputs
The data at the B bus are displayed at the A bus
The data at the B bus ar displayed at the A bus.
The data of the B bus are stored to the internal
flip-flop on low to high transition of th clock pulse
X* X X H
Qn
X*
XH
L
H
X
The data stored to the internal flip-flop are dispayed
at the A bus
L
The data at the B bus are stored to the internal flip-
H
flop on low to high transition of the clock pulse. The
states of the internal flip-flops output directly to the
A bus
INPUTS OUTPUTS The A bus are inputs and the B bus are outputs
X X* L X
L
H
L
The data at the A bus are displayed at the B bus
H
HH
X* L X
L
H
L
The data at the A bus are displayed at the B bus.
H
The data of the A bus are stored to the internal flip-
flop on low to high transition of the clock pulse
X X* H X
X
X* H X
L
H
Qn
The data stored to the internal flip-flops are
displayed at the B bus
L
the data at the A bus are stored to the internal flip-
H
flop on low to high transition of the clock pulse. The
states of the internal flip-flops output directly to the
B bus
OUTPUTS OUTPUTS Both the A bus and the B bus are outputs
XXHH
Qn
Qn
The data stored to the internal flip-flops are
HL
displayed at the A and B bus respactively
HH
Qn
Qn
The output at the A bus are displayed at the B bus,
the output at the B bus are displayed at the A bus
respectively
X : DON’T CARE
Z : HIGH IMPEDANCE
Qn : THE DATA STORED TO THE INTERNAL FLIP-FLOPS BY MOST RECENT LOW TO HIGH TRANSITION OF THE CLOCK INPUTS
* : THE DATA AT THE A AND B BUS WILL BE STORED TO THE INTERNAL FLIP-FLOPS ON EVERY LOW TO HIGH TRANSITION OF
THE CLOCK INPUTS
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