dm74als646 Fairchild Semiconductor, dm74als646 Datasheet - Page 2

• Manufacturer Part Number: dm74als646
• Description: Dm74als646 Octal 3-state Bus Transceiver And Register
• Manufacturer: Fairchild Semiconductor

www.fairchildsemi.com
Connection Diagram
Function Table
H
L
X
H/L
Note 1: The data output functions may be enabled or disabled by various signals at the G and DIR inputs. Data input functions are always enabled, i.e., data
at the bus pins will be stored on every LOW-to-HIGH transition on the clock inputs.
Logic Diagram
LOW Logic Level
Positive going edge of pulse
HIGH Logic Level
Don’t Care (Either LOW or HIGH Logic Levels including transitions)
Either LOW or HIGH Logic Level excluding transitions
G
H
H
X
X
L
L
L
L
DIR CAB CBA SAB SBA
H
H
X
X
X
X
L
L
H/L
H/L
X
X
X
X
Inputs
H/L
H/L
X
X
X
X
X
X
X
X
X
X
H
L
X
X
X
X
H
X
X
L
Not Specified
A1 thru A8
Output
Output
Input
Input
Input
Input
Input
Data I/O (Note 1)
2
Not Specified Store A, B Unspecified
B1 thru B8
Output
Output
Input
Input
Input
Input
Input
Store B, A Unspecified
Store A and B Data
Isolation, Hold Storage
Real-Time B Data to a Bus
Stored B Data to a Bus
Real-Time A Data to B Bus
Stored A Data to B Bus
Operation or Function