Functionally Equivalent to AMD’s AM29821
Provide Extra Data Width Necessary for
Wider Address/Data Paths or Buses With
Parity
Outputs Have Undershoot-Protection
Circuitry
Power-Up High-Impedance State
Buffered Control Inputs to Reduce
dc Loading Effects
Package Options Include Plastic
Small-Outline (DW) Packages, Ceramic
Chip Carriers (FK), and Standard Plastic
(NT) and Ceramic (JT) 300-mil DIPs

description
These 10-bit flip-flops feature 3-state outputs
designed specifically for driving highly capacitive
or relatively low-impedance loads. They are
particularly suitable for implementing wider buffer
registers, I/O ports, bidirectional bus drivers with
parity, and working registers.
The ten flip-flops are edge-triggered D-type
flip-flops. On the positive transition of the clock
(CLK) input, the Q outputs are true to the data (D)
input.
A buffered output-enable (OE) input can be used
to place the ten outputs in either a normal logic
state (high or low logic levels) or a highimpedance
state. In the high-impedance state, the
outputs neither load nor drive the bus lines
significantly. The high-impedance state and
increased drive provide the capability to drive bus
lines without interface or pullup components.
OE does not affect the internal operation of the flip-flops. Previously stored data can be retained or new data
can be entered while the outputs are in the high-impedance state.
The SN54AS821A is characterized for operation over the full military temperature range of –55°C to 125°C. The
SN74AS821A is characterized for operation from 0°C to 70°C.