Bandwidth Selection Timing
The transceiver is in default SIR/
MIR mode when powered on.
User needs to apply the following
programming sequence to both
the SD and TXD inputs to enable
the transceiver to operate at FIR
mode.
V
IH
SD/MODE
V
IL
t
S
t
H
V
IH
SD/MODE
50%
50%
V
IL
t
S
t
H
V
IH
TXD
50%
50%
V
IL
TXD
50%
50%
V
IL
Figure 3. Bandwidth selection timing at SIR/MIR mode.
Figure 4. Bandwidth selection timing at FIR mode.
Setting the transceiver to SIR/MIR
Mode (9.6 kb/s to 1.152 Mbit/s)
1. Set SD/Mode input to logic
HIGH
2. TXD input should remain at
logic LOW
3. After waiting for t
S
≥
25 ns,
set SD/Mode to logic LOW, the
HIGH to LOW negative edge
transition will determine the
receiver bandwidth
4. Ensure that TXD input remains
low for t
H
≥
100 ns, the
receiver is now in SIR/MIR
mode
5. SD input pulse width for mode
selection should be > 50 ns.
Setting the transceiver to FIR
(4.0 Mbit/s) Mode
1. Set SD/Mode input to logic
HIGH
2. After SD/Mode input remains
HIGH at > 25ns, set TXD input
to logic HIGH, wait t
S
≥
25 ns
(from 50% of TXD rising edge
till 50% of SD falling edge)
3. Then set SD/Mode to logic
LOW, the HIGH to LOW
negative edge transition will
determine the receiver
bandwidth
4. After waiting for t
H
≥
100ns, set
the TXD input to logic LOW
5. SD input pulse width mode
selection should be > 50ns.
4
AGILENT [ AGILENT TECHNOLOGIES, LTD. ]
