Debugging an ARM core which is not 1st on JTAG chain
Technical Note 17681
5/17/2022 8:08 AM
This technical note provides information about how to debug a device that is not first in the JTAG chain.
When the device is not first in the JTAG chain, C-SPY® needs information about the preceding devices. Use an I-jet® probe and the
EmuDiag.exe tool to collect such information.
Example of a JTAG chain
A chain of connected JTAG devices is created by consecutively connecting TDO on one device to TDI on thenext device, and so on.
This schematic shows two devices connected in a JTAG chain.
Which device is the first device?
The first device (for this purpose), is the device where
TDO is connected to the debug probe. Note that:
- The first device will be given the ID
- When debugging the first device, there is no need to make extra settings.
Debugging a device that is not first in the JTAG chain
These steps are needed to debug a device that is not first in the JTAG chain. (In this example the JTAG chain consists of a Toshiba TMPM320-SK board and an ST STM32F207ZG board.)
- Connect the I-jet probe.
- Start IAR Embedded Workbench for Arm®, and choose I-jet > EmuDiag.
EmuDiag.execlikc the Test JTAG button. (This displays the JTAG Configuration dialog box.)
- Click the Autodetect button to see this JTAG chain:
- Note down this information:
- The ST STM32F207ZG has the ID TAP1
- The device at TAP0 (the Toshiba TMPM320) has IR=4. In other words, four preceding bits.
- In Embedded Workbench for Arm, open the project for ST STM32F207ZG, and choose Project > Options > Debugger > I-jet > Interface
- Make these settings:
- Set Probe config to Explicit
- Multitarget debug system
- Set Target number to 1
- JTAG scan chain contains non-Arm devices
- Set Preceding bits to 4
- Click the Setup tab to select the Reset strategy:
- For Cortex select Core reset.
- For ARM 7/9 select Software reset.
- It is important to choose a reset strategy that does not use TRST to reset, because such a reset will reset all cores.
- For I-jet and
EmuDiag.exethere is more information about the JTAG chain in
- For J-Link, read
Typical path is
C:\Program Files\IAR Systems\Embedded Workbench x.y\
Where x.y stands for version of the common components.
The I-jet probe can connect to any device in a JTAG chain. Connect the I-jet, use the
EmuDiag.exe tool to collect information about the JTAG chain and enter that information in C-SPY Debugger Options dailog box.
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