• Functionally Equivalent to AMD’s AM29821
• Provide Extra Data Width Necessary for
Wider Address/Data Paths or Buses With
• Outputs Have Undershoot-Protection
• 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
10-BIT BUS-INTERFACE FLIP-FLOPS
WITH 3-STATE OUTPUTS
SDAS230A – DECEMBER 1983 – REVISED AUGUST 1995
SN54AS821A . . . JT PACKAGE
SN74AS821A . . . DW OR NT PACKAGE
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)
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 high-
impedance 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.
SN54AS821A . . . FK PACKAGE
4 3 2 1 28 27 26
12 13 14 15 16 17 18
NC – No internal connection
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.
OE CLK D
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
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Copyright © 1995, Texas Instruments Incorporated