TFBS5711 VISHAY [Vishay Siliconix], TFBS5711 Datasheet - Page 8

• Manufacturer Part Number: TFBS5711
• Description: Fast Infrared Transceiver Module (MIR, 1.152 Mbit/s) for IrDA
• Manufacturer: VISHAY [Vishay Siliconix]

TFBS5711
Vishay Semiconductors
I/O and Software
In the description, already different I/Os are men-
tioned. Different combinations are tested and the
function verified with the special drivers available
from the I/O suppliers. In special cases refer to the I/
O manual, the Vishay application notes, or contact
directly Vishay Sales, Marketing or Application.
Programming
Pulse duration Switching
After Power-on the TFBS5711 is in the default short
Rxd pulse duration mode.
Some ENDECs are not able to decode short pulses
as valid SIR pulses. Therefore an additional mode
with extended pulse duration (same as in standard
SIR transceivers) is added in TFBS5711. TFBS5711
is set to the "short output pulse" as default after power
on, and after recovering from the shutdown mode (SD
being active longer than 1.5 ms).
To switch the transceivers from the short Rxd pulse
duration mode to the long pulse duration mode and
vice versa, follow the procedure described below.
Setting to the ENDEC compatibility mode
with an Rxd pulse duration of 2 s
1. Set SD input to logic "HIGH".
2. Set Txd input to logic "HIGH". Wait t
3. Set SD to logic "LOW" (this negative edge latches
state of Txd, which determines speed setting).
4. After waiting t
After that Txd is enabled as normal Txd input and the
Rxd output is set for the longer Rxd - pulse duration
mode.
Setting back to the default mode with a
400 ns pulse duration
1. Set SD input to logic "HIGH".
2. Set Txd input to logic "LOW". Wait t
3. Set SD to logic "LOW" (this negative edge latches
state of Txd, which determines speed setting).
www.vishay.com
8
h
200 ns.
s
s
200 ns.
200 ns.
4. After waiting t
"LOW". The hold time of Txd is limited by the maxi-
mum allowed pulse length.
After that Txd is now enabled as normal Txd input and
the Rxd output is set for the short Rxd - pulse duration
mode.
The timing of the pulse duration changing procedure
is quite uncritical. However, the whole change must
not take more than 600 s. See in the spec. "Shut-
down Active Time Window for Programming"
Simplified Method
Setting the device to the long pulse duration is simply
applying a short active (less than 600 s) pulse to SD
(Txd = Low). In any case a short SD pulse will force
the device to leave the default mode and go the com-
patibility mode. Vice versa applying a 1.5 ms (mini-
mum) pulse at SD will cause the device to go back to
the default mode by activating a power-on-reset and
setting the device to the default short pulse mode.
This simplified method takes more time but may be
easier to handle.
Figure 2. Timing Diagram for changing the output pulse duration
18150
TxD 50%
SD
h
t s
200 ns Txd can be set to logic
50%
t h
50%
Document Number 82634
High:
Low:
Rev. 1.3, 05-Dec-03
VISHAY
400 ns
2 µs