SLAAEH8 October   2024 AFE781H1 , AFE782H1 , AFE881H1 , AFE882H1 , DAC8740H , DAC8741H , DAC8742H

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
    1. 1.1 The 4-20mA Loop
    2. 1.2 The HART Protocol
      1. 1.2.1 Adding HART to the 4-20mA Loop
      2. 1.2.2 HART FSK
  5. 2AFE881H1 HART Modem
    1. 2.1 AFE881H1 HART Transmitter
    2. 2.2 Detailed Schematic
      1. 2.2.1 Input Protection
      2. 2.2.2 Startup Circuit
      3. 2.2.3 Voltage-to-Current Stage
      4. 2.2.4 Voltage-to-Current Calculation
      5. 2.2.5 HART Signal Transmission
      6. 2.2.6 HART Input Protection
      7. 2.2.7 Current Consumption
      8. 2.2.8 HART Transmitter Board
      9. 2.2.9 HART Protocol Stack
  6. 3HART Testing and Registration
    1. 3.1  HART History and the FieldComm Group
    2. 3.2  HART Testing Overview
      1. 3.2.1 HART Protocol Specifications
      2. 3.2.2 HART Protocol Test Specifications
      3. 3.2.3 Remote Transmitter Device Testing
    3. 3.3  HART Test Equipment
    4. 3.4  HART Physical Layer Testing
      1. 3.4.1 FSK Sinusoid Test
      2. 3.4.2 Carrier Start and Stop Time Tests
      3. 3.4.3 Carrier Start and Stop Transient Tests
      4. 3.4.4 Output Noise During Silence
      5. 3.4.5 Analog Rate of Change Test
      6. 3.4.6 Receive Impedance Test
      7. 3.4.7 Noise Sensitivity Test
      8. 3.4.8 Carrier Detect Test
    5. 3.5  Data Link Layer Tests
      1. 3.5.1 Data Link Layer Test Specifications
      2. 3.5.2 Data Link Layer Test Logs
    6. 3.6  Universal Command Tests
    7. 3.7  Common-Practice Command Tests
    8. 3.8  Device Specific Command Tests
    9. 3.9  HART Protocol Test Submission
    10. 3.10 HART Registration
  7. 4Other TI HART Modem Designs
  8. 5Summary
  9. 6Acknowledgments
  10. 7References

3.5.1 Data Link Layer Test Specifications

HCF_SPEC-081 defines the token-passing data link layer specification. The DLL is responsible for the reliable, error free communication of data between HART compatible devices. This document specifies the rules used by HART products to communicate digital information over a physical link.

To test the DLL, the test specifications are outlined by HCF_TEST-1. These tests cover:

  • HART communication frame detection and recognition by the transmitter
  • Frame generation from the transmitter for reception by the controller
  • Bus arbitration to check that the transmitter responds promptly after receiving a command, and sending commands in burst mode
  • Data link layer services that control bytes sent in the data frame for the application layer

The Linux-based HART test system has a set of pre-programmed tests to verify the data link layer. For all DLL tests, the HART test system runs the test and records a log of the test and results. In the HART test system, the hartmenu command gives a list of different tests available. These tests can be run consecutively, where the tests are run one after another until user intervention is required. Alternately, tests can be run individually, where the user can select a specific test.

Table 3-9 shows a list of data link layer tests.

Table 3-9 DLL Test List and Results
TEST NUMBER DESCRIPTION RESULT
DLL001 FSK preamble check Pass
DLL002 Delimiter check Pass
DLL003 Frame expansion check Pass
DLL004 Short frame check Pass
DLL005 HART controller address bit check Pass
DLL006 Burst mode bit check Pass
DLL007 Long frame address check Pass
DLL009 Incorrect byte count check Pass
DLL010 Vertical parity check Pass
DLL011 Framing error check Pass
DLL012 Check byte test Pass
DLL013 FSK gap receive timeout test Pass
DLL014 Long message test Pass
DLL015 Start of message in data field check Pass
DLL016 Preamble check for BACK frames Pass
DLL017 Preamble check for ACK frames Pass
DLL018 Gap errors in ACK frames check Pass
DLL019 Gap check for BACK frames Pass
DLL020 Dribble byte check for ACK frames Pass
DLL021 Dribble byte check for BACK frames Pass
DLL022 Test host address bit for BACK frames Pass
DLL023 Test burst mode bit of burst-mode transmitter device frames Pass
DLL024 Test transmitter device responds within STO Pass
DLL025 Burst hold during HART controller preamble Pass
DLL026 Test burst response time after a DUT ACK Pass
DLL027 Test response time between consecutive bursts Pass
DLL028 BACK timing with STXs errors Pass
DLL029 Burst mode timeout on other transmitter device Pass
DLL030 Burst after response from other transmitter device Pass
DLL032 Read unique identifier Pass
DLL033 Write polling address Pass
DLL034 Read unique identifier with tag (Command 11) Pass
DLL035 Write number of response preambles Pass
DLL038 Read unique identifier with tag (Command 21) Pass
DLL039 Transmitter device time-out stress test Pass
DLL040 Unique address test Pass
DLL041 Framing successive messages Pass
DLL042 Command number expansion Pass

The DLL tests with the exception of DLL039 take about 13 hours to complete. Near the end of the run, there are a few tests that require user intervention to cycle power on the devices.

DLL039 is the final DLL test to be run. In this time-out stress test, the tester sends 2 million consecutive commands and records the log with any errors in the response from the device. Because HART communication responds at about 1 command per second, this test takes about 19 days to complete. An uninterrupted power supply is highly recommended when running this test.