8-bit universal shift/storage register (3-State) 74F299
FEATURES
• Common parallel I/O for reduced pin count
• Additional serial inputs and outputs for expansion
• Four operating modes: Shift left, shift right, load and store
• 3-State outputs for bus-oriented applications
DESCRIPTION
The 74F299 is an 8-bit universal shift/storage register with 3-State
outputs. Four modes of operation are possible: Hold (store), shift
left, shift right and parallel load. The parallel load inputs and flip-flop
outputs are multiplexed to reduce the total number of package pins.
Additional outputs are provided for flip-flops Q0 and Q7 to allow
easy serial cascading. A separate active-Low Master Reset is used
to reset the register.
The 74F299 contains eight edge-triggered D-type flip-flops and the
interstage logic necessary to perform synchronous shift left, shift
right, parallel load and hold operations. The type of operation is
determined by S0 and S1, as shown in the Function Table. All
flip-flop outputs are brought out through 3-State buffers to separate
I/O pins that also serve as data inputs in the parallel load mode.
Q0 and Q7 are also brought out on other pins for expansion in serial
shifting of longer words.
A Low signal on MR overrides the Select and CP inputs and resets
the flip-flops. All other state changes are initiated by the rising edge
of the clock. Inputs can change when the clock is in either state
provided only that the recommended setup and hold times, relative
to the rising edge of clock are observed.
A High signal on either OE0 or OE1 disables the 3-State buffers and
puts the I/O pins in the high impedance state. In this condition the
shift, hold, load and reset operations can still occur. The 3-State
buffers are also disabled by High signals on both S0 and S1 in
preparation for a parallel load operation.
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