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Developer’s Manual March, 2003 13-43
Intel
®
80200 Processor based on Intel
®
XScale
™
Microarchitecture
Software Debug
13.14.5 Dynamically Loading IC After Reset
An external host can load code into the instruction cache “on the fly” or “dynamically”. This
occurs when the host downloads code while the processor is not being reset. However, this requires
strict synchronization between the code running on the Intel
®
80200 processor and the external
host. The guidelines for downloading code during program execution must be followed to ensure
proper operation of the processor. The description in this section focuses on using a debug handler
running on the Intel
®
80200 processor to synchronize with the external host, but the details apply
for any application that is running while code is dynamically downloaded.
To dynamically download code during software debug, there must be a minimal debug handler
stub, responsible for doing the handshaking with the host, resident in the instruction cache. This
debug handler stub should be downloaded into the instruction cache during processor reset using
the method described in Section 13.14.4. Section 13.14.5.1, Dynamic Code Download
Synchronization describes the details for implementing the handshaking in the debug handler.
Figure 13-14 shows a high level view of the actions taken by the host and debug handler during
dynamic code download.
Figure 13-14. Downloading Code in IC During Program Execution
DBGRX
JTAG IR
DBGTX
LDIC
wait for handler to signal
download code
signal handler
Handler begins execution
signal host ready
wait for host to signal
download is complete
continue execution.
ready to start download
for download
download complete
Debugger Actions
Debug Handler Actions
clock
15 TCKs