FUNCTION TRUTH TABLES
INPUTS
RE
X
X
X
X
DE
0
DI
0
X
X
LINE
CONDITION
No Fault
No Fault
X
Fault
OUTPUTS
A
0
Z
Z
B
0
Z
Z
INPUTS
RE
0
0
0
DE
0
0
0
0
A-B
+0.2V
-0.2V
Inputs Open
X
OUTPUTS
R
0
Z
Table 1. Transmit Function Truth Table
Table 2. Receive Function Truth Table
SWITCHING WAVEFORMS
DE
+3V
0V
5V
V
OL
V
OH
0V
2.3V
t
ZH
f = 1MHz; t
R
< 10ns; t
F
< 10ns
1.5V
t
ZL
2.3V
Output normally LOW
Output normally HIGH
1.5V
t
LZ
0.5V
0.5V
t
HZ
A,
B
A,
B
Figure 6. Driver Enable and Disable Times
A– B
V
OD2
+
V
OD2
–
V
OH
V
OL
t
PHL
f = 1MHz; t
R
≤ 10ns ; t
F
≤ 10ns
0V
INPUT
0V
R
1.5V
OUTPUT
t
PLH
1.5V
Figure 7. Receiver Propagation Delays
RE
+3V
0V
5V
V
IL
V
IH
1.5V f = 1MHz; t ≤ 10ns; t ≤ 10ns
R
F
t
ZL
1.5V
Output normally LOW
Output normally HIGH
1.5V
t
LZ
0.5V
0.5V
t
HZ
R
R
0V
1.5V
t
ZH
Figure 8. Receiver Enable and Disable Times
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 50-668-707 • www.exar.com
SP48E,485E_00_2808
6
EXAR [ EXAR CORPORATION ]
