Datasheet

SN54HC652, SN74HC652
OCTAL BUS TRANSCEIVERS AND REGISTERS
WITH 3-STATE OUTPUTS
SCLS151E – DECEMBER 1982 – REVISED MARCH 2003
2
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
description/ordering information (continued)
Data on the A or B data bus, or both, can be stored in the internal D-type flip-flops by low-to-high transitions at
the appropriate clock (CLKAB or CLKBA) terminals, regardless of the select- or output-control terminals. When
SAB and SBA are in the real-time transfer mode, it is possible to store data without using the internal D-type
flip-flops by simultaneously enabling OEAB and OEBA
. In this configuration, each output reinforces its input.
When all other data sources to the two sets of bus lines are at high impedance, each set of bus lines remains
at its last state.
To ensure the high-impedance state during power up or power down, OEBA
should be tied to V
CC
through a
pullup resistor, and OEAB should be tied to GND through a pulldown resistor; the minimum value of the resistor
is determined by the current-sinking/current-sourcing capability of the driver.
FUNCTION TABLE
INPUTS
DATA I/O
†
OPERATION OR FUNCTION
OEAB OEBA CLKAB CLKBA SAB SBA A1–A8 B1–B8
OPERATION
OR
FUNCTION
L H H or L H or L X X Input Input Isolation
L H ↑↑X X Input Input Store A and B data
X H ↑ H or L X X Input Unspecified
‡
Store A, hold B
H H ↑↑X
‡
X Input Output Store A in both registers
L X H or L ↑ X X Unspecified
‡
Input Hold A, store B
L L ↑↑XX
‡
Output Input Store B in both registers
L L X X X L Output Input Real-time B data to A bus
L L X H or L X H Output Input Stored B data to A bus
H H X X L X Input Output Real-time A data to B bus
H H H or L X H X Input Output Stored A data to B bus
H L H or L H or L H H Output Output
Stored A data to B bus and
stored B data to A bus
†
The data-output functions are enabled or disabled by a variety of level combinations at OEAB or OEBA
. Data-input functions always are enabled;
i.e., data at the bus terminals is stored on every low-to-high transition on the clock inputs.
‡
Select control = L: clocks can occur simultaneously.
Select control = H: clocks must be staggered to load both registers.