Datasheet

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SLLS513A − AUGUST 2001 − REVISED MARCH 2004
4
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
timing
Figure 1 shows how the two independent serial ports can be enabled or disabled. As shown by the logic states,
depending on the FORCEOFF
, FORCEON, and receiver input levels, either port can be powered down.
Intermediate receiver input levels indicate a 0-V input. Also, it is assumed a pulldown resistor to ground is used
for the receiver outputs. The INV
pin goes low when its respective receiver input does not supply a valid RS-232
level. For simplicity, voltage levels, timing differences, and input/output edge rates are not shown.
DINB
DINA
RIN2B
RIN2A
FORCEON
FORCEOFFB
FORCEOFFA
ROUT2A
ROUT2A
ROUT2B
ROUT2B
DOUTA
DOUTB
INVA
INVB
0
V
0
V
0
V
0
V
NOTES: A. Ports A and B manually powered off
B. Port A manually powered off, port B in normal operation with auto-powerdown enabled
C. Port B powered off by auto-powerdown, port A in normal operation with auto-powerdown enabled
D. Port A in normal operation with auto-powerdown disabled, port B manually powered off
E. Ports A and B in normal operation with auto-powerdown disabled
A B C D E
Figure 1. Timing Diagram