BDM Operation

The CMD912X board will emulate supported HC12 device internal flash memory in external ram. This feature allows BDM (Background Debug Modules) such as the AX-BDM12 to load and control the execution of code being developed without the necessity of the internal flash memory being programmed many times during the development process. This feature improves updating time and allows the use of may software breakpoints instead of being limited to only 2 hardware breakpoints.

Operation Notes for BDM use:

1)CMD912x CONFIG SWITCH should be set 1 ON, 2 OFF, 3 OFF, and 4 ON. Position 5 should be Off unless the DG/DT128 Fixed Page is desired to be emulated in ram. These settings provide external ram and PRU operation with the ECS enabled for Paging emulation.

2)PM12xxx MODE SWITCH is usually set for positions 1 and 2 off to select Single Chip Mode. This setting forces the BDM Monitor in the HC12 active immediately after Reset with the BDM connected which is desired for most BDM pods. The BDM can then load a script to set the desired operating mode and configuration, see next note. The DP256 version should have Mode Switch position 3 ON for correct operation of the MODC select buffer during RESET.

3)The BDM initialization of the HC12 should set the correct operating MODE (Expanded Wide for memory access) and enable port emulation for the PRU to operate. The EME, EMK, LSTRB, RW, IVIS, ROMEN and Stretch configuration bits should be set for proper memory map and PRU operation. The external RAM does not require any cycle stretch for accesses up to 25MHz E clock. The Axiom support CD contains sample set-up macros for the AX-BDM12.