How do I set the TFDU6300 to operate in SIR mode (2.4 kbps)?

* Question

How do I set the TFDU6300 to operate in SIR mode (2.4 kbps)?

* Answer

The TFDU6300 infrared transceiver supports multiple operating modes, and SIR mode (2.4 kbps to 115.2 kbps) is the standard low-bandwidth mode. According to the device datasheet, the module enters SIR mode by default after power-up.
If you need to explicitly configure or re-enter SIR mode, you can use the SD (Shutdown) and TXD pins to issue the correct mode-selection sequence.

1. Default Behavior

• The TFDU6300 starts in SIR mode automaticallyon power-up.
• No special configuration is required unless the device has been switched to FIR or VFIR mode.

2. Procedure to Force SIR Mode

To manually configure the device into SIR (lower-bandwidth) mode, follow the steps below:

Step-by-step mode-setting sequence

1. Set SD = HIGH
   This initiates the configuration window.
2. Pull TXD = LOW and hold ≥ 200 ns
   The state of TXD determines the operating mode.

• LOW = SIR mode
• HIGH = FIR (high-speed) mode

3. Drive SD = LOW
   The falling edge of SD latches the TXD state.
4. Hold TXD = LOW for at least another 200 ns
   This completes the mode selection.

After this sequence, the TFDU6300 will operate in SIR mode.

3. Important Notes

• If the SD pulse is too long (several microseconds), the device may interpret it as shutdown, not mode selection.
• Timing requirements (≥200 ns) must be met to prevent undefined behavior.
• This mode-selection method only applies when the device has already left SIR mode or when you need deterministic control in system initialization.

Summary

The TFDU6300 normally powers up in SIR mode without user intervention. When a forced configuration is required, set TXD low, toggle SD high → low within the timing window, and the device will re-enter SIR mode. This ensures compatibility with low-speed IrDA communication at 2.4 kbps and related data rates.