mc9s12xs128 Freescale Semiconductor, Inc, mc9s12xs128 Datasheet - Page 169

• Manufacturer Part Number: mc9s12xs128
• Description: Hcs12 Microcontrollers 16-bit Automotive Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

5.1.2.3
The BDM can be used until all bus masters (e.g., CPU or XGATE or others depending on which masters
are available on the SOC) are in stop mode. When CPU is in a low power mode (wait or stop mode) all
BDM firmware commands as well as the hardware BACKGROUND command can not be used
respectively are ignored. In this case the CPU can not enter BDM active mode, and only hardware read and
write commands are available. Also the CPU can not enter a low power mode during BDM active mode.
If all bus masters are in stop mode, the BDM clocks are stopped as well. When BDM clocks are disabled
and one of the bus masters exits from stop mode the BDM clocks will restart and BDM will have a soft
reset (clearing the instruction register, any command in progress and disable the ACK function). The BDM
is now ready to receive a new command.
5.1.3
A block diagram of the BDM is shown in
5.2
A single-wire interface pin called the background debug interface (BKGD) pin is used to communicate
with the BDM system. 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.
Freescale Semiconductor
System
Host
External Signal Description
Block Diagram
Low-Power Modes
Register Block
BKGD
BDMSTS
Register
BDMACT
ENBDM
CLKSW
UNSEC
TRACE
SDV
Interface
Serial
S12XS Family Reference Manual, Rev. 1.10
Control
Data
Figure 5-1. BDM Block Diagram
Figure
Standard BDM Firmware
16-Bit Shift Register
Secured BDM Firmware
Instruction Code
LOOKUP TABLE
LOOKUP TABLE
5-1.
Execution
and
Background Debug Module (S12XBDMV2)
Bus Interface
Control Logic
and
Address
Data
Control
Clocks
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