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7604-0001EA
SD
Shutdown
Receive
Transmit
RX Light
IRRX
IRTX
TX Light
TR
TSD
TD
TR
TD
TR
AC Timing:
Device Operation:
The operating mode of the transceiver is controlled by the
SD (shutdown) input and the state of the transmitter input.
The device is enabled whenever the SD input is a logic low.
If the SD input is high IRTX is opened and the IRRXʼ output
is tri-stated and the device is said to be shutdown. If the SD
input is low half duplex operation is enabled. Care must be
taken to ensure that the transmitter input is low when not
transmitting (idle), this enables the receiver. Table 1 sum-
marizes the operating modes. Once the transmit input is
toggled (or from the last bit transmitted) the receiver is not
active for the recovery time, TR. The receive data output
Table 1:
SD input
IRTX input
IrLED
Receiver
IRRX Output
0
0
Off
Enabled
Valid Data
0
Toggling
Toggling
Disabled, for T
R min
Tri-State
1
x
Off
Shutdown
Tri-State
may be valid after the recovery time provided there is
received light.
The MS3201s transmitter LED (IrLED) radiant inten-
sity is proportional to the forward current (I
F) through
IrLED. System power consumption can be optimized
for each application by selection of an appropriate
external current limiting resistor. Transmit distance
may be approximated using the following equation;
D (meters) = √(I
F(amps)/0.3)
Current limiting resistors should be ±2% tolerance, non
inductive (not wire wound) type.
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