mc9s12xd256 Freescale Semiconductor, Inc, mc9s12xd256 Datasheet - Page 569

• Manufacturer Part Number: mc9s12xd256
• Description: Hcs12x Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Chapter 15
Background Debug Module (S12XBDMV2)
15.1
This section describes the functionality of the background debug module (BDM) sub-block of the
HCS12X core platform.
The background debug module (BDM) sub-block is a single-wire, background debug system implemented
in on-chip hardware for minimal CPU intervention. All interfacing with the BDM is done via the BKGD
pin.
The BDM has enhanced capability for maintaining synchronization between the target and host while
allowing more flexibility in clock rates. This includes a sync signal to determine the communication rate
and a handshake signal to indicate when an operation is complete. The system is backwards compatible to
the BDM of the S12 family with the following exceptions:
15.1.1
The BDM includes these distinctive features:
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TAGGO command no longer supported by BDM
External instruction tagging feature now part of DBG module
BDM register map and register content extended/modified
Global page access functionality
Enabled but not active out of reset in emulation modes
CLKSW bit set out of reset in emulation mode.
Family ID readable from firmware ROM at global address 0x7FFF0F (value for HCS12X devices
is 0xC1)
Single-wire communication with host development system
Enhanced capability for allowing more flexibility in clock rates
SYNC command to determine communication rate
GO_UNTIL command
Hardware handshake protocol to increase the performance of the serial communication
Active out of reset in special single chip mode
Nine hardware commands using free cycles, if available, for minimal CPU intervention
Hardware commands not requiring active BDM
14 firmware commands execute from the standard BDM firmware lookup table
Introduction
Features
MC9S12XDP512 Data Sheet, Rev. 2.17
569