August 1999
Revised September 2000
74ACT652
Transceiver/Register
General Description
The ACT652 consists of bus transceiver circuits with D- type flip-flops, and control circuitry arranged for multiplexed transmission of data directly from the input bus or from internal registers. Data on the A or B bus will be clocked into the registers as the appropriate clock pin goes to the HIGH logic level. Output Enable pins (OEAB, OEBA) are provided to control the transceiver function.
Features
■Independent registers for A and B buses
■Multiplexed real-time and stored data
■Outputs source/sink 24 mA
■TTL-compatible inputs
Ordering Code:
Order Number |
Package Number |
Package Description |
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74ACT652SC |
M24B |
24-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-013, 0.300 Wide |
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74ACT652MTC |
MTC24 |
24-Lead Thin Shrink Small Outline Package (TSSOP), JEDEC MO-153, 4.4mm Wide |
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74ACT652SPC |
N24C |
24-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 Wide |
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Device also available in Tape and Reel. Specify by appending suffix letter “X” to the ordering code.
Logic Symbols |
Connection Diagram |
IEEE/IEC |
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Pin Descriptions
Pin Names |
Description |
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A0–A7, B0–B7 |
A and B Inputs/3-STATE Outputs |
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CPAB, CPBA |
Clock Inputs |
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SAB, SBA |
Select Inputs |
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OEAB, |
OEBA |
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Output Enable Inputs |
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FACT is a trademark of Fairchild Semiconductor Corporation.
Transceiver/Register 74ACT652
© 2000 Fairchild Semiconductor Corporation |
DS500310 |
www.fairchildsemi.com |
74ACT652
Function Table
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Inputs |
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Inputs/Outputs (Note 1) |
Operating Mode |
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OEAB |
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OEBA |
CPAB |
CPBA |
SAB |
SBA |
A0 thru A7 |
B0 thru B7 |
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L |
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H |
H or L |
H or L |
X |
X |
Input |
Input |
Isolation |
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L |
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H |
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X |
X |
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Store A and B Data |
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X |
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H |
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H or L |
X |
X |
Input |
Not Specified |
Store A, Hold B |
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H |
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H |
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X |
X |
Input |
Output |
Store A in Both Registers |
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L |
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X |
H or L |
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X |
X |
Not Specified |
Input |
Hold A, Store B |
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L |
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L |
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X |
X |
Output |
Input |
Store B in Both Registers |
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L |
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L |
X |
X |
X |
L |
Output |
Input |
Real-Time B Data to A Bus |
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L |
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L |
X |
H or L |
X |
H |
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Store B Data to A Bus |
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H |
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H |
X |
X |
L |
X |
Input |
Output |
Real-Time A Data to B Bus |
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H |
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H |
H or L |
X |
H |
X |
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Stored A Data to B Bus |
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H |
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L |
H or L |
H or L |
H |
H |
Output |
Output |
Stored A Data to B Bus and |
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Stored B Data to A Bus |
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H = HIGH Voltage Level |
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L = LOW Voltage Level |
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X = Immaterial |
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= LOW-to-HIGH Clock Transition |
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Note 1: The data output functions may be enabled or disabled by various signals at OEAB or OEBA 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
Please note that this diagram is provided only for the understanding of logic operations and should not be used to estimate propagation delays.
www.fairchildsemi.com |
2 |
Functional Description
In the transceiver mode, data present at the HIGH impedance port may be stored in either the A or B register or both.
The select (SAB, SBA) controls can multiplex stored and real-time.
The examples in Figure 1 demonstrate the four fundamental bus-management functions that can be performed with the Octal bus transceivers and receivers.
Note A: Real-Time
Transfer Bus B to Bus A
OEAB |
OEBA |
CPAB |
CPBA |
SAB |
SBA |
L |
L |
X |
X |
X |
L |
Note C: Storage
Data on the A or B data bus, or both can be stored in the internal D-type flip-flop by LOW to HIGH transitions at the appropriate Clock Inputs (CPAB, CPBA) regardless of the Select or Output Enable Inputs. When SAB and SBA are in the real time transfer mode, it is also 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. Thus when all other data sources to the two sets of bus lines are in a HIGH impedance state, each set of bus lines will remain at its last state.
Note B: Real-Time
Transfer Bus A to Bus B
OEAB |
OEBA |
CPAB |
CPBA |
SAB |
SBA |
H |
H |
X |
X |
L |
X |
Note D: Transfer Storage
Data to A or B
OEAB |
OEBA |
CPAB |
CPBA |
SAB |
SBA |
OEAB |
OEBA |
CPAB CPBA |
SAB |
SBA |
X |
H |
X |
X |
X |
H |
L |
H or L H or L |
H |
H |
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L |
X |
X |
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X |
X |
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L |
H |
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X |
X |
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FIGURE 1. |
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74ACT652
3 |
www.fairchildsemi.com |
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