| Copyright © 2002, 2003 ARM Limited. All rights reserved. | ARM DDI 0275D |
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| Home > Introduction > About the Embedded Trace Buffer |
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As process speeds increase it is increasingly difficult to obtain trace information off a chip from an Embedded Trace Macrocell (ETM). This causes difficulties in maintaining acceptable signal quality or the signals have to be demultiplexed on to what can become a very large number of trace port pins.
The solution is to provide a buffer area on-chip where the trace information is stored, and read from the chip later, at a slower rate.
The ETB11 stores data produced by the ETM11RV. The buffered data can then be accessed by the debugging tools using a JTAG (IEEE 1149.1) interface, as shown in Figure 1.1.
Providing an on-chip buffer enables the trace data generated by the ETM11RV (at the system clock rate) to be read by the debugger at a reduced clock rate. This removes the requirement for high-speed pads for the trace data.
This buffered data can also be accessed through an AHB slave-based AHB interface included as part of the ETB11. This enables software running on the processor to read the trace data generated by the ETM11RV.
The major blocks shown in Figure 1.1 are:
The ETM11RV monitors the ARM core buses and passes compressed information in real time to the ETB11 where it is stored for later retrieval. The data is then passed through the JTAG trace port to an interface unit. This is an external hardware device that passes the information from the trace port to a debugging tool, for example, a PC. The debug tool:
retrieves data from the interface unit
reconstructs a historical view of processor activity including data accesses
configures the macrocell through the JTAG interface unit and port.
User-definable filters enable you to limit the amount of information captured in search of a bug, reducing upload time from the trace port analyzer.
EmbeddedICE is a JTAG-based debugging environment for ARM microprocessors. EmbeddedICE provides the interface between the ARM source-level symbolic debugger, ARMxd, and an ARM microprocessor embedded within any ASIC. The ARMxd debugger is available for PC compatible and Sun workstation platforms.
EmbeddedICE provides:
real-time address and data-dependent breakpoints
single stepping
full access and control of the ARM CPU
access to the ASIC system.
EmbeddedICE also enables the embedded microprocessor to access the host system peripherals, for instance screen display, keyboard input and disk drive storage.
Boundary scan is a methodology enabling complete controllability and observability of the boundary pins of a JTAG-compatible device by software control. This capability enables in-circuit testing without requiring specially designed in-circuit test equipment.
| Copyright © 2002, 2003 ARM Limited. All rights reserved. | ARM DDI 0275D |
| Non-Confidential | |
| PDF version | |
| Home > Introduction > About the Embedded Trace Buffer |