Truth Table
(Continued)
Inputs
Data I/O
Operation or Function
G
DIR
CAB
CBA
SAB
SBA
A1 Thru A8
B1 Thru B8
’ALS646, ’ALS647
’AS646
’ALS648, ’ALS649
’AS648
L
L
L
L
X
X
X
X
X
X
L
H
Output
Input
Real-Time B Data to A Bus
Stored B Data to A Bus
Real-Time B Data to A Bus
Stored B Data to A Bus
L
L
H
H
X
X
X
X
L
H
X
X
Input
Output
Real-Time A Data to B Bus
Stored A Data to B Bus
Real-Time A Data to B Bus
Stored A Data to B Bus
H
e
High Level L
e
Low Level X
e
Irrelevant
u
e
low-to-high level transition
The data output functions i.e., data at the bus pins may be enabled or disabled by various signals at the G and DIR inputs. Data input functions are always enabled.
The data output functions i.e., data at the bus pins will be stored on every low-to-high transition on the clock inputs.
AC Electrical Characteristics
MM54HC646/MM74HC646, MM54HC648/MM74HC648
V
CC
e
5V, T
A
e
25
§
C, t
r
e
t
f
e
6 ns
Symbol
Parameter
Conditions
Typ
Guaranteed
Limit
30
Units
f
MAX
Maximum Operating
Frequency
Maximum Propagation
Delay, A or B Input
to B or A Output
Maximum Propagation
Delay, CBA or CAB
Input to A or B Output
Maximum Propagation
Delay, SBA or SAB Input to A
or B Output, with A or B high
Maximum Propagation
Delay, SBA or SAB Input to A
or B Output, with A or B low
Maximum Enable
Time G or DIR Input to
A or B Output
Maximum Disable
Time, G or DIR Input to
A or B Output
45
MHz
t
PHL
, t
PLH
C
L
e
45 pF
14
25
ns
t
PHL
, t
PLH
C
L
e
45 pF
31
40
ns
t
PHL
, t
PLH
C
L
e
45 pF
35
50
ns
t
PHL
, t
PLH
C
L
e
45 pF
35
50
ns
t
PZH
, t
PZL
R
L
e
1 k
X
C
L
e
45 pF
18
33
ns
t
PHZ
, t
PLZ
R
L
e
1 k
X
C
L
e
5 pF
17
30
ns
AC Electrical Characteristics
MM54HC646/MM74HC646, MM54HC648/MM74HC648
V
CC
e
2.0–6.0V, C
L
e
50 pF, t
r
e
t
f
e
6 ns (unless otherwise specified)
T
A
e
25
§
C
74HC
54HC
Symbol
Parameter
Conditions
V
CC
T
A
eb
40 to 85
§
C
Guaranteed Limits
4
21
24
189
250
37
50
31
44
275
338
55
68
47
59
T
A
eb
55 to 125
§
C
Units
Typ
f
MAX
Maximum Operating
Frequency
C
L
e
50 pF
2.0V
4.5V
6.0V
2.0V
2.0V
4.5V
4.5V
6.0V
6.0V
2.0V
2.0V
4.5V
4.5V
6.0V
6.0V
5
3
18
20
225
300
45
60
39
53
330
405
66
81
57
71
MHz
MHz
MHz
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
27
31
180
200
30
40
26
35
220
270
44
54
38
47
t
PHL
, t
PLH
Maximum Propagation
Delay, A or B Input
to B or A Output
C
L
e
50 pF
C
L
e
150 pF
C
L
e
50 pF
C
L
e
150 pF
C
L
e
50 pF
C
L
e
150 pF
C
L
e
50 pF
C
L
e
150 pF
C
L
e
50 pF
C
L
e
150 pF
C
L
e
50 pF
C
L
e
150 pF
60
80
21
30
18
22
110
150
31
40
28
34
t
PHL
, t
PLH
Maximum Propagation
Delay, CBA or CAB
Input to A or B Output
3