Atmel AT91EB01, Руководство пользователя

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The Debugging System
2-2 AT91EB01 Evaluation Board User Manual
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The EmbeddedICE macrocell to provide access to the extensions from the outside
world
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The ARM EmbeddedICE interface, to provide communication between the
EmbeddedICE macrocell and the debugger resident on the host computer
The EmbeddedICE macrocell is the integrated on-chip logic that provides debug support
for the ARM7TDMI processor. The EmbeddedICE macrocell is programmed in serial
through the Test Access Port (TAP) controller on the ARM7TDMI, via the JTAG inter-
face. This is usually achieved via the EmbeddedICE interface. The EmbeddedICE
macrocell consists of two real-time watchpoint units, together with a control and status
register. One or both watchpoint units can be programmed to halt the execution of
instructions by the ARM7TDMI.
The ARM EmbeddedICE interface is a JTAG protocol conversion unit. This translates
the debug protocol messages generated by the debugger into JTAG signals that can be
sent to the EmbeddedICE macrocell, and vice versa. The interface can be connected to
the host computer using either the built-in serial port, or the built-in serial and parallel
ports. The serial port is used for bidirectional transfers, but the parallel port is only used
to download code. Using the parallel port increases the maximum download speed with
EmbeddedICE to approximately 20K bytes/s. This is considerably greater than using the
serial ports alone (even at 38400 baud), and so is the recommended method of using
EmbeddedICE (host permitting).
Although EmbeddedICE is generally non-intrusive, there are two exceptions:
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When an ARM debugger is started, it attempts to find out the state of the target
microcontroller. To do this, it halts the target and inspects the state of the ARM
registers. This, however, can be considered non-intrusive if the debugging session
begins after the debugger has been started.
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Watchpoints on structures or arrays that are larger than one word may cause the
target microcontroller to halt execution when writes occur close to the watchpointed
area. EmbeddedICE will restart execution transparently to the user, but this may still
cause problems if the application is real-time.
Note: The Debug Comms Channel is currently not supported on the AT91EB01
board.
2.1.3 Multi-ICE Multi-ICE is the latest ICE-compatible debug solution from Advanced RISC Machines. It
comprises an interface unit which connects between the parallel port of a PC and the
JTAG interface and software to allow an ARM debugger to communicate with the inter-
face unit.
The Multi-ICE system is very similar to EmbeddedICE except that the Embedded ICE
interface unit contains a processor and software, whereas the Multi-ICE interface unit
contains no processor and the interface software runs on the host PC. There are a num-
ber of advantages to this approach - a smaller, lighter interface unit with a lower power
consumption (it can be target powered), easier updating of software, more flexible
interfaces.
Features of Multi-ICE:
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Stored/Automatic configuration
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Networked connections
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High-performance code download
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Low-voltage target operation
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Small, lightweight unit improves ease of use
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Additional power supply not normally required (powered from target)
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Easy-to-use parallel port connection