Development Support
MC1321x Reference Manual, Rev. 1.6
21-2
Freescale Semiconductor
21.2
Background Debug Controller (BDC)
All MCUs in the HCS08 Family contain a single-wire background debug interface that supports in-circuit
programming of on-chip nonvolatile memory and sophisticated non-intrusive debug capabilities. Unlike
debug interfaces on earlier 8-bit MCUs, this system does not interfere with normal application resources.
It does not use any user memory or locations in the memory map and does not share any on-chip
peripherals.
BDC commands are divided into two groups:
•
Active background mode commands require that the target MCU is in Active Background Mode
(the user program is not running). Active background mode commands allow the CPU registers to
be read or written, and allow the user to trace one user instruction at a time, or GO to the user
program from Active Background Mode.
•
Non-intrusive commands can be executed at any time even while the user’s program is running.
Non-intrusive commands allow a user to read or write MCU memory locations or access status and
control registers within the background debug controller.
Typically, a relatively simple interface pod is used to translate commands from a host computer into
commands for the custom serial interface to the single-wire background debug system. Depending on the
development tool vendor, this interface pod may use a standard RS-232 serial port, a parallel printer port,
or some other type of communications such as a universal serial bus (USB) to communicate between the
host PC and the pod. The pod typically connects to the target system with ground, the BKGD pin, RESET,
and sometimes V
DD
.
NOTE
On MCUs where the RESET pin is not input-only, an open-drain connection
to reset allows the host to force a target system reset, which is useful to
regain control of a lost target system or to control start up of a target system
before the on-chip non volatile memory has been programmed.
On MCUs where RESET pin is input-only, the RESET pin can only provide
a reset into user mode.
Sometimes V
DD
can be used to allow the pod to use power from the target system to avoid the need for a
separate power supply. However, if the pod is powered separately, it can be connected to a running target
system without forcing a target system reset or otherwise disturbing the running application program.
Figure 21-1. BDM Tool Connector
2
4
6
NO CONNECT 5
NO CONNECT 3
1
RESET
1
BKGD
GND
V
DD
1
On MCUs where RESET is an input only, the RESET
pin can only provide a reset into user mode. To enter
active BDM mode use the background debug force
Содержание freescale semiconductor MC13211
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