SPRACM3E August   2021  – January 2023 TMS320F280021 , TMS320F280021-Q1 , TMS320F280023 , TMS320F280023-Q1 , TMS320F280023C , TMS320F280025 , TMS320F280025-Q1 , TMS320F280025C , TMS320F280025C-Q1 , TMS320F280033 , TMS320F280034 , TMS320F280034-Q1 , TMS320F280036-Q1 , TMS320F280036C-Q1 , TMS320F280037 , TMS320F280037-Q1 , TMS320F280037C , TMS320F280037C-Q1 , TMS320F280038-Q1 , TMS320F280038C-Q1 , TMS320F280039 , TMS320F280039-Q1 , TMS320F280039C , TMS320F280039C-Q1 , TMS320F280040-Q1 , TMS320F280040C-Q1 , TMS320F280041 , TMS320F280041-Q1 , TMS320F280041C , TMS320F280041C-Q1 , TMS320F280045 , TMS320F280048-Q1 , TMS320F280048C-Q1 , TMS320F280049 , TMS320F280049-Q1 , TMS320F280049C , TMS320F280049C-Q1 , TMS320F28384D , TMS320F28384S , TMS320F28386D , TMS320F28386S , TMS320F28388D , TMS320F28388S , TMS320F28P650DH , TMS320F28P650DK , TMS320F28P650SH , TMS320F28P650SK , TMS320F28P659DK-Q1

 

  1.   Using the Fast Serial Interface (FSI) With Multiple Devices in an Application
  2.   Trademarks
  3. 1Introduction to the FSI Module
  4. 2FSI Applications
  5. 3Handshake Mechanism
    1. 3.1 Daisy-Chain Handshake Mechanism
    2. 3.2 Star Handshake Mechanism
  6. 4Sending and Receiving FSI Data Frames
    1. 4.1 FSI Data Frame Configuration APIs
    2. 4.2 Start Transmitting Data Frames
  7. 5Daisy-Chain Topology Tests
    1. 5.1 Two Device FSI Communication
      1. 5.1.1 CPU Control
      2. 5.1.2 DMA Control
      3. 5.1.3 Hardware Control
    2. 5.2 Three Device FSI Communication
      1. 5.2.1 CPU/DMA Control
      2. 5.2.2 Hardware Control
        1. 5.2.2.1 Skew Compensation for Three Device Daisy-Chain System
          1. 5.2.2.1.1 CPU/DMA control
          2. 5.2.2.1.2 Hardware Control
  8. 6Star Topology Tests
  9. 7Event Synchronization Over FSI
    1. 7.1 Introduction
      1. 7.1.1 Requirement of Event Sync for Distributed Systems
      2. 7.1.2 Solution Using FSI Event Sync Mechanism
      3. 7.1.3 Functional Overview of FSI Event Sync Mechanism
    2. 7.2 C2000Ware FSI EPWM Sync Examples
      1. 7.2.1 Location of the C2000Ware Example Project
      2. 7.2.2 Summary of Software Configurations
        1. 7.2.2.1 Lead Device Configuration
        2. 7.2.2.2 Node Device Configuration
      3. 7.2.3 1 Lead and 2 Node F28002x Device Daisy-Chain Tests
        1. 7.2.3.1 Hardware Setup and Configurations
        2. 7.2.3.2 Experimental Results
      4. 7.2.4 1 Lead and 8 Node F28002x Device Daisy-Chain Tests
        1. 7.2.4.1 Hardware Setup and Configurations
        2. 7.2.4.2 Experimental Results
      5. 7.2.5 Theoretical C2000 Uncertainties
    3. 7.3 Additional Tips and Usage of FSI Event Sync
      1. 7.3.1 Running the Example
      2. 7.3.2 Target Configuration File
      3. 7.3.3 Usage of Event Sync for Star Configuration
  10. 8References
  11. 9Revision History

7.2.5 Theoretical C2000 Uncertainties

The event jitter as described in the earlier sections is a result of the uncertainties in the oscillator clocks from device to device, transmission distance between the devices, digital isolators and/or differential device disturbance, and so forth. Additional uncertainty is also induced by the synchronism from FSIRX to the CLB module to FSITX signal path configured inside the device, shown in Figure 7-14.

Figure 7-14 Internal C2000 FSI Event Trigger Path

Along the internal C2000 FSI event trigger path the clock domain changes between FSI RX clock, device SYSCLK (CLB clock), and the FSI TX clock. Each time the signal moves from one clock domain to another it encounters a synchronizer that adds some amount of variable cycle delay (not the same number each time). The theoretical cycle count uncertainty of the event trigger path from section 1 to 4 shown in Figure 7-14 is described below.

Path 1-2: FSI Ping frame being received at RX module to generation of the PING_PKT_RCVD signal. Clock domain change from FSI RX CLK to SYSCLK is made resulting in 0-2 SYSCLK cycles of uncertainty.

Path 2-3: Ping_PKT_RCVD signal passing through the CLB module to externally trigger the FSI TX module to send a Ping frame. Clock domain change from SYSCLK to FSI TX CLK is made resulting in 0-2 SYSCLK cycles of uncertainty.

Path 3-4: FSI TX external trigger to FSI TX ping frame generation. Clock domain change from SYSCLK (CLB Clock) to FSI TX CLK is made resulting in 0-2 FSI TX CLK cycles of uncertainty.

From the above the total worst-case theoretical cycle uncertainty can be calculated:

Note: Total Worst-Case Theoretical Cycle Uncertainty = 4 SYSCLK cycles + 2 FSI TXCLK cycles.

For a device operating at a SYSCLK frequency of 100 MHz, the theoretically calculated amount of jitter induced will be around 40 nanoseconds, assuming TXCLK is the same as SYSCLK. The practical value achieved will be a small fraction of the calculated theoretical value because this is the worst-case theoretical consideration. The possibility of observing this worst-case value is statistically low for any device in a network topology. This can be seen in the experimental results shown earlier, where the actual jitter measured for 8 node devices is measured to be 75 nanoseconds while the theoretical worst case will be 320 nanoseconds, considering 40 nanoseconds of jitter induced per device in the chain.