Motorola M68EVB912B32, User Manual

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OPERATION
68EVB912B32UM/D 3-2
This mode is effected using the MCU’s PAD0 line. User code may be programmed into byte-
erasable EEPROM using the D-Bug12 commands listed in 3.5.3 Command-Set Summary.
Control can be returned to D-Bug12 in the following ways:
1. Move the jumpers on headers W3 and W4 to position 0 and reset the EVB.
2. Terminate the user program with code that returns to D-Bug12 after execution has
finished.
To return to D-Bug12 automatically after a user program has finished, include the following lines
as the last instructions to be executed in the program:
STACKTOP: equ $0c00 ; stack at top of on-chip RAM
AltResetVect: equ $F7FE
;
lds #STACKTOP
jmp [AltResetVect,PCR] ; jump to start of D-Bug12
3.1.3 POD (Probe) Mode
In this mode (W3-0 and W4-1), the EVB and D-Bug12 serve as a POD ("probe") interface
between a target system and the user. Communications between the EVB and the target are by
means of the Background Debug Mode (BDM) interface, using the EVB header W12 (BDM
OUT).
This arrangement allows the target system to perform true emulation of an application, as the
BDM interface is non-intrusive upon the target’s foreground operation. The target’s on-chip
resources are all available for the application. The target may be a second M68EVB912B32
board or any other M68HC12 system. D-Bug12 commands are entered as usual on the user
terminal, which is served by the POD EVB.
3.1.3.1 Target Types Supported
All members of the M68HC12 family may be used in the target system.
3.1.3.2 Target MCU Characteristics
The following D-Bug12 commands must be used to inform D-Bug12 of the target MCU’s
essential operating characteristics in order to allow transparent modification of the target’s
EEPROM. For details, refer to the command descriptions in 3.6 D-Bug12 Command Set.
DEVICE

specifies the target’s microprocessor type
EEBASE

specifies the base address of the target’s Flash EEPROM
REGBASE

specifies the base address of the target MCU’s I/O registers