Features
• Buffered Inputs
• Four Operating Modes: Shift Left, Shift Right, Load
and Store
• Can be Cascaded for N-Bit Word Lengths
• I/O0 - I/O7 Bus Drive Capability and Three-State for
Bus Oriented Applications
• Typical fMAX = 50MHz at VCC = 5V, CL = 15pF, TA = 25oC
• Fanout (Over Temperature Range)
- Standard Outputs . . . . . . . . . . . . . . . 10 LSTTL Loads
- Bus Driver Outputs . . . . . . . . . . . . . 15 LSTTL Loads
• Wide Operating Temperature Range . . . -55oC to 125oC
• Balanced Propagation Delay and Transition Times
• Significant Power Reduction Compared to LSTTL
Logic ICs
• HC Types
- 2V to 6V Operation
- High Noise Immunity: NIL = 30%, NIH = 30% of VCC
at VCC = 5V
• HCT Types
- 4.5V to 5.5V Operation
- Direct LSTTL Input Logic Compatibility,
VIL= 0.8V (Max), VIH = 2V (Min)
- CMOS Input Compatibility, Il ≤ 1μA at VOL, VOH

Description
The ’HC259 and ’HCT299 are 8-bit shift/storage registers
with three-state bus interface capability. The register has four
synchronous-operating modes controlled by the two select
inputs as shown in the mode select (S0, S1) table. The mode
select, the serial data (DS0, DS7) and the parallel data (I/O0
- I/O7) respond only to the low-to-high transition of the clock
(CP) pulse. S0, S1 and data inputs must be stable one setup
time prior to the clock positive transition.
The Master Reset (MR) is an asynchronous active low input.
When MR output is low, the register is cleared regardless of
the status of all other inputs. The register can be expanded
by cascading same units by tying the serial output (Q0) to
the serial data (DS7) input of the preceding register, and
tying the serial output (Q7) to the serial data (DS0) input of
the following register. Recirculating the (n x 8) bits is
accomplished by tying the Q7 of the last stage to the DS0 of
the first stage.
The three-state input/output I(/O) port has three modes of
operation:
1. Both output enable (OE1 and OE2) inputs are low and S0
or S1 or both are low, the data in the register is presented
at the eight outputs.
2. When both S0 and S1 are high, I/O terminals are in the
high impedance state but being input ports, ready for parallel
data to be loaded into eight registers with one clock
transition regardless of the status of OE1 and OE2.
3. Either one of the two output enable inputs being high will
force I/O terminals to be in the off-state. It is noted that
each I/O terminal is a three-state output and a CMOS
buffer input.