Datasheet

Table Of Contents
Background Debug Module
MC9S12DP256 — Revision 1.1
Background Debug Module (BDM)
BDM disabled when secure feature is enabled
Block Diagram The block diagram of the BDM is shown in Figure 136 below.
Figure 136 BDM Block Diagram
Interface Signals
A single-wire interface pin is used to communicate with the BDM system.
Two additional pins are used for instruction tagging.
BKGD — Background interface pin
TAGHI
— High byte instruction tagging pin
TAGLO
— Low byte instruction tagging pin
BKGD and TAGHI
share the same pin. TAGLO and LSTRB share the
same pin.
Background
Interface Pin
(BKGD)
Debugging control logic communicates with external devices serially via
the single-wire background interface pin (BKGD). During reset, this pin
is a mode select input which selects between normal and special modes
of operation. After reset, this pin becomes the dedicated serial interface
pin for the background debug mode.
ENBDM
CLKSW
BDMACT
ENTAG
TRACE
SDV
16-BIT SHIFT REGISTER
BKGD
CLOCKS
DATA
ADDRESS
HOST
SYSTEM
BUS INTERFACE
AND
CONTROL LOGIC
AND EXECUTION
INSTRUCTION DECODE
LOOKUP TABLE
Standard BDM firmware
Freescale Semiconductor, I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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