SPRAD62 February   2023 TMS320F280023C , TMS320F280025C , TMS320F280025C-Q1 , TMS320F280037C , TMS320F280037C-Q1 , TMS320F280038C-Q1 , TMS320F280039C , TMS320F280039C-Q1 , TMS320F28386D , TMS320F28386D-Q1 , TMS320F28386S , TMS320F28386S-Q1 , TMS320F28388D , TMS320F28388S , TMS320F28P650DH , TMS320F28P650DK , TMS320F28P650SH , TMS320F28P650SK , TMS320F28P659DK-Q1

 

  1.   Abstract
  2.   Trademarks
  3. 1Introduction
  4. 2Serial Port Design Methodology
    1. 2.1 Step 1: Understand Design Requirements
    2. 2.2 Step 2: Identify Required Inputs to the CLB Tile
      1. 2.2.1 GPIO Input Qualification
      2. 2.2.2 CLB Input Settings
    3. 2.3 Step 3: Identify Required Outputs from CLB Logic
      1. 2.3.1 Synchronizing Outputs Signals
      2. 2.3.2 Output Signal Conditioning
    4. 2.4 Step 4: Design the CLB Logic
      1. 2.4.1 Resource Allocation
      2. 2.4.2 Exchanging Data Between CLB FIFOs and MCU RAM
      3. 2.4.3 CLB Logic Status and Trigger Flags
        1. 2.4.3.1 Status/Flag Bits
        2. 2.4.3.2 Trigger Bits
    5. 2.5 Step 5: Simulate the Logic Design
    6. 2.6 Step 6: Test the CLB Logic
  5. 3Example A: Using the CLB to Input and Output a TDM Stream in Audio Applications
    1. 3.1 Example Overview
    2. 3.2 Step 1: Understand Design Requirements
    3. 3.3 Step 2: Identify Required Inputs to the CLB Tile
    4. 3.4 Step 3: Identify Required Outputs from CLB Logic
    5. 3.5 Step 4: Design the CLB Logic
      1. 3.5.1 Resource Allocation
      2. 3.5.2 TDM Word Counter
      3. 3.5.3 FSYNC and DATA1 Output Synchronization
    6. 3.6 Step 5: Simulate the Logic Design
    7. 3.7 Step 6: Test the CLB Logic
      1. 3.7.1 Hardware Setup and Connections
      2. 3.7.2 Software Setup
      3. 3.7.3 Testing Output Setup and Hold Times
      4. 3.7.4 Testing Data Integrity
  6. 4Example B: Using the CLB to Implement a Custom Communication Bus for LED Driver in Lighting Applications
    1. 4.1 Example Overview
    2. 4.2 Step 1: Understand Design Requirements
    3. 4.3 Step 2: Identify Required Inputs to the CLB Tile
    4. 4.4 Step 3: Identify Required Outputs From CLB Logic
    5. 4.5 Step 4: Design the CLB Logic
      1. 4.5.1 TX Tile Logic
      2. 4.5.2 RX Tile Logic
      3. 4.5.3 Data Clocking
    6. 4.6 Step 5: Simulate the Logic Design
    7. 4.7 Step 6: Test the CLB Logic
      1. 4.7.1 Hardware Setup and Connections
      2. 4.7.2 Software Setup
      3. 4.7.3 Testing Output Setup and Hold Times
  7. 5References

3.7.3 Testing Output Setup and Hold Times

A key consideration in the output TDM stream from the CLB is the expected setup and hold time seen by the receiving device. To measure the setup and hold time, an oscilloscope was used to continuously capture the output of the CLB. Figure 3-15 shows the TDM output without the latch and delay logic added to the FSYNC_OUT and DATA1_OUT signals. The setup and hold time of DATA1_OUT with respect to BCLK_OUT reduced due to the delay in the DATA1_OUT signal.

GUID-20220916-SS0I-ZBRB-QMNP-ZSKHFRVFVBX2-low.png Figure 3-15 TDM-8 Output Without Latch and Delay Logic

The oscilloscope plot shown in Figure 3-16 shows the final TDM output with the latch and delay logic added to the FSYNC_OUT and DATA1_OUT signals. The setup and hold time are greatly improved using this approach.

GUID-20220916-SS0I-QLKN-GD0J-F0M3VMV5SPGW-low.png Figure 3-16 Final TDM-8 Output

Since BCLK_OUT must be passed through the CLB tile without jitter, it is not possible to accurately control the timing between BCLK_OUT and the other two signals without introducing jitter on BCLK_OUT. However, in this case, the setup and hold time are acceptable. If needed the BCLK_OUT signal can be inverted using the AOC in the CLB tile to trade setup for hold time.

Finally note the 10 ns jitter on the FSYNC_OUT and DATA1_OUT signals. This is due to the CLB tile sampling the incoming BCLK_IN signal at 100 MHz. The jitter reduces the setup and hold time further.