74F651A Datasheet, PDF (5/14 Pages) NXP Semiconductors – Transceivers/registers

Philips Semiconductors
Transceivers/registers
Product specification
74F651A/74F652A
The following examples demonstrate the four fundamental
bus-management functions that can be performed with the 74F651A
and 74F652A. The select pins determine whether data is stored or
BUS MANAGEMENT FUNCTIONS
REAL TIME BUS TRANSFER
BUS B TO BUS A
REAL TIME BUS TRANSFER
BUS A TO BUS B
transferred through the device in real time. The output enable pins
determine the direction of the data flow.
STORAGE FROM
A, B, OR A AND B
TRANSFER STORED DATA
TO A AND/OR B
BUS A
BUS B
BUS A
BUS B
BUS A
BUS B
BUS A
BUS B
OEAB OEBA CPAB CPBA SAB SBA
L
LX
X XL
OEAB OEBA CPAB CPBA SAB SBA
H H X X LX
OEAB OEBA CPAB CPBA SAB SBA
X H↑
L
XX
LH↑
X XX
↑ XX
↑ XX
OEAB OEBA CPAB CPBA SAB SBA
H
L H or L H or L H H
SF00409
FUNCTION TABLE
INPUTS
DATA I/O
OPERATING MODE
OEAB OEBA CPAB CPBA SAB SBA
An
Bn
74F651A
74F652A
L
H H or L H or L X
X
Input
Input
Isolation
Isolation
L
H
↑
↑
X
X
Input
Input
Store A and B data
Store A and B data
X
H
↑ H or L X
X
Input
Unspecified*
Store A, hold B
Store A hold B
H
H
↑
↑
L
X
Input
Output
Store A in both registers Store A in both registers
L
X H or L ↑
X
X Unspecified*
Input
Hold A, store B
Hold A, store B
L
L
↑
↑
X
L
Output
Input
Store B in both registers Store B in both registers
L
L
X
X
X
L
Output
Input
Real time B data to A bus Real time B data to A bus
L
L
X H or L X
H
Output
Input
Stored B data to A bus
Stored B data to A bus
H
H
X
X
L
X
Input
Output
Real time A data to B bus Real time A data to B bus
H
H H or L X
H
X
Input
Output
Stored A data to B bus
Stored A data to B bus
H
L H or L H or L H
H
Output
Output
Stored A data to B bus
Stored A data to B bus
H
L H or L H or L H
H
Output
Output
Stored B data to A bus
Stored B data to A bus
Notes to function table
1. H = High-voltage level
2. L = Low-voltage level
3. * = The data output function may be enabled or disabled by various signals at the OEBA and OEAB inputs. Data input functions are
always enabled, i.e., data at the bus pins will be stored on every low-to-high transition of the clock.
4. ↑ = Low-to-high clock transition
5. X = Don’t care
1999 Jun 23
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