
Determining the Core and System State
Copyright 2000-2001 by LSI Logic Corporation. All rights reserved.
9-27
9.5.5 Debug Request
A debug request can take place through the EmbeddedICE-RT logic or
by asserting the EDBGRQ signal. The request is synchronized and
passed to the processor. A debug request takes priority over any pending
interrupt. Following synchronization, the processor core enters the debug
state after the instruction that is currently in the execute stage finishes
both the memory and write stages. While waiting for the instruction to
complete, the processor allows no more instructions to enter the execute
stage.
Note:
If EDBGRQ is asserted while the processor is operating in
monitor mode, the processor enters the debug state as if
operating in halt mode.
9.5.6 Actions of the ARM9E-S in Debug State
When the ARM9E-S is in the debug state, both memory interfaces
indicate internal cycles. This ensures that the tightly coupled SRAM
within the ARM946E-S and the AHB interface are both quiescent,
allowing the rest of the AHB system to ignore the ARM9E-S and function
normally. Because the rest of the system continues operation, the
ARM9E-S ignores aborts and interrupts.
The nRESET signal must be held stable during debug. If the system
applies reset to the ARM946E-S (nRESET is driven LOW), the state of
the ARM9E-S changes without the debugger knowing about it.
9.6 Determining the Core and System State
When the ARM946E-S is in the debug state, you can examine the core
and system state by forcing Load and Store Multiple instructions into the
instruction pipeline.
Before you examine the core and system state, the debugger must check
the EmbeddedICE-RT Debug Status register (bit 4) and determine
whether the processor entered debug from the Thumb state or the ARM
state. When bit 4 is HIGH, it indicates the processor was in the Thumb
state. When bit 4 is LOW, the processor was in the ARM state.