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JTAG Device Chain

The JTAG Device Chain section displays one or more debug targets connected through the JTAG interface. The IDCODE, Device Name, and IR Length are displayed automatically for each device.

Target Driver Setup - JTAG Device Chain

Manual Configuration allows identifying undetected JTAG devices. Specify the instruction register length (IR len) of each device in the JTAG device chain.

AP specifies the identifier of the Access Port in multi-core devices with a single Debug Port (DP). The Access Port specification depends on the Arm Debug Interface (ADI) supported in the device.

  • For APv1 (ADIv5):
    • The AP value range is 0 to 255.
    • For single core devices, set AP to 0 (default).
    • For a multi-core device, core 0 is expected to have AP=0 and core 1 AP=1. However, the port identifiers are specified by the device manufacturer.
  • For APv2 (ADIv6):
    • The AP value range is 0x00000000 to 0xFFFFFFFF. The value needs to be set by a user for a target sub-system based on the information provided by the device vendor in documentation.
    • If AP value is set to 0xFFFFFFFF then µVision will automatically connect to the AP of the first auto-detected CPU.
    • JTAG daisy chain with mix of ADIv5 and ADIv6 aren't supported.
    • Debugger automatically requests power using Granular Power Requester (GPR) from Class 0x9 ROM Tables.
    • Only top-level APs are supported, not "nested APs" (AP exposing its registers via target memory accesses of a higher-level AP).

If AP contains an invalid identifier, the error message "Invalid ROM Table" is shown whenever a debuging session is started.


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