mc68336 Freescale Semiconductor, Inc, mc68336 Datasheet - Page 26

• Manufacturer Part Number: mc68336
• Description: An Introduction To The Mc68331 And Mc68332
• Manufacturer: Freescale Semiconductor, Inc

3.1 Communicating with the Target Board
After a target board has been built, it is generally necessary to communicate with it for debugging purposes.
Although a designer can write a ROM monitor or modify CPU32Bug to communicate with the MCU via the
serial port, it is simpler and often more effective to use an emulator or the CPU32 background debug mode
(BDM) for communication.
3.1.1 Using an Emulator
An emulator is a direct replacement for the chip that is used to evaluate both software and signals on the
target board. Emulators can be very sophisticated and costly, but are very useful in tracking down design
problems because they allow the designer to see exactly what the MCU is doing at every step of operation.
When both the board and code are fully debugged, the emulator is removed and the MCU is placed on the
board.
3.1.2 Using Background Debug Mode
Background debug mode is a special CPU operating mode that allows an external host to take control of
the MCU. BDM is a very useful tool for debugging. During BDM operation, normal instruction execution is
suspended, and microcode executes built-in debugging instructions under external control. Since BDM sus-
pends processor execution, an external host can examine and change memory and registers. BDM instruc-
tions and the protocol required to use them are described in detail in the CPU32 Reference Manual
(CPU32RM/AD). A BDM Driver Package for Modular Microcontrollers (AN1230/D), shows how to imple-
ment a BDM communication interface using C-language drivers.
While a BDM interface is relatively easy to implement, ready-made BDM interfaces are inexpensive and re-
liable. Freescale sells the M68ICD32 BDM debugger made by P&E Microcomputer Systems. The M68ICD32
consists of the necessary cable and software to implement BDM debugging on an IBM-compatible PC. All
the discussions in this section assume that M68ICD32 is being used.
3.1.2.1 BDM Signals
To use BDM, simply connect ten MCU lines to pins on the development board that are spaced so that a
female Berg connector can plug into them. Figure 17 shows the pinouts for the recommended 10-pin BDM
connector. Table 4 describes the BDM signals. Refer to 3.2.1.2 Using the EVK in Background Debug
Mode for a discussion of the older, 8-pin connector.
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3 ESTABLISHING COMMUNICATION
Freescale Semiconductor, Inc.
For More Information On This Product,
Figure 17 10-Pin BDM Connector
RESET
GND
GND
VDD
Go to: www.freescale.com
DS
1
3
5
7
9
2
4
6
8
10
BERR
BKPT/DSCLK
FREEZE
IFETCH/DSI
IPIPE/DSO
M68331/332TUT/D
MC68331/332
332TUT BERG10