Analog Devices ADSP-2189M EZ-KIT Lite, Manual

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Standard Operations
2-8 ADSP-2189M EZ-KIT Lite Evaluation System Manual
Halt loop
The monitor program idles in the halt loop when the program is not run-
ning user code. While there, you can
READ
and
WRITE
memory and
registers, download programs, set breakpoints, change the UART’s baud
rate, and single step through your code. To enter the halt loop from code,
you must suspend or stop the code, using either a breakpoint or a
HALT
instruction. At this point, the halt loop polls the UART. With every char-
acter received from the UART, the command-processing kernel verifies
whether a full command has been received. If a full command has been
received, the kernel processes the command; otherwise, control is returned
to the halt loop to wait for more characters. The only method of executing
your code once the halt loop has been entered is to send a
RUN
or
SINGLE
STEP
command in the debugger.
UART ISR
The UART Interrupt Service Routine (
Timer
ISR) is entered when your
code is running, but the host is still interacting with the board. As the host
sends bytes, the UART ISR takes the data stream from the UART and
builds the command. As with the halt loop, each character received is
passed to the command-processing kernel. Unlike the halt loop, the mon-
itor returns to your code immediately after the interrupt is serviced.
#
The following restrictions should be observed to ensure correct
board operation.
• The host loses contact with the monitor while the user program is
running if the user program disables the
Timer
interrupt or changes
the
Timer
interrupt vector.