SLAA202B February   2005  – December 2018 MSP430F149 , MSP430F149 , MSP430F2252-Q1 , MSP430F2252-Q1 , MSP430F2272-Q1 , MSP430F2272-Q1 , MSP430F2274 , MSP430F2274 , MSP430FG4619 , MSP430FG4619

 

  1.   Implementing IrDA With MSP430™ MCUs
    1.     Trademarks
    2. 1 Introduction
    3. 2 Hardware Description
      1. 2.1 Hardware Overview
      2. 2.2 Circuit Description
    4. 3 Software Description
      1. 3.1 Implementing IrPHY Layer Using Timer_A
        1. 3.1.1 Transmission
        2. 3.1.2 Reception
      2. 3.2 Implementing IrPHY Layer using USCI_A0
      3. 3.3 Implementing IrLAP
        1. 3.3.1 Discovery Services
        2. 3.3.2 Connect Services
        3. 3.3.3 Data Services
        4. 3.3.4 Disconnect Services
      4. 3.4 Implementing IrLMP
        1. 3.4.1 Discovery Services
        2. 3.4.2 Link Connect and Connect Services
        3. 3.4.3 Data Services
        4. 3.4.4 Disconnect Services
      5. 3.5 IAS Implementation
      6. 3.6 TTP Implementation
      7. 3.7 IrCOMM Implementation
      8. 3.8 Application Layer
    5. 4 PC Demonstration Application
    6. 5 IrDA Protocol Basics
      1. 5.1 Physical (IrPHY) Layer
      2. 5.2 Link Access Protocol (IrLAP) Layer
      3. 5.3 Link Management Protocol (IrLMP) Layer
      4. 5.4 Information Access Services (IAS)
      5. 5.5 Tiny Transfer Protocol (TTP)
      6. 5.6 IrCOMM
    7. 6 IrDA Communication Diagram
    8. 7 Frame Exchange Log
    9. 8 References
  2.   Revision History

3.6 TTP Implementation

The operation of TTP involves the exchange of data TTP-PDUs (protocol data units). Effectively, this adds a single octet of header to the IrLMP-MUX data LM-PDUs. This additional octet is used to convey increments (credits) to the number of data TTP-PDUs that may be exchanged in each direction using the underlying IrLMP service.

In this implementation, a simple policy for advancing credit is used. This means that the credit is held longer at AvailCredit rather than being advanced at the earliest opportunity. This leaves buffers available to be reclaimed and redeployed to other needy TTP connections or to relieve resource problems elsewhere in a system.

Connect TTP-PDUs exchanged during connection establishment are not regarded as requiring or consuming credit. Segmentation and reassembly is not implemented. Because the IrLAP window size is equal to 1, a single TTP connection can take full advantage of the underlying IrLAP window.

For this particular implementation, when the initial TTP connection frame is identified, credit is issued so that the peer entity can transfer its data. As soon as the MSP430 responds and after it has received an RR command from the primary, it then issues more credit for the peer entity to continue transmitting data.