Microcontroller User's Manual

29-34 MCF5282 User’s Manual MOTOROLA
Background Debug Mode (BDM)
As an example, any BDM read of an accumulator register (ACCn) must be preceded by two
commands accessing the MAC status register. Specifically, the following BDM sequence
is required:
BdmReadACCn (
rcreg macsr; // read macsr contents & save
wcreg #0,macsr; // disable all rounding modes
rcreg accn; // read the desired accumulator
wcreg #saved_data,macsr;// restore the original macsr
)
Likewise, the following BDM sequence is needed to write an accumulator register:
BdmWriteACCn (
rcreg macsr; // read macsr contents & save
wcreg #0,macsr; // disable all rounding modes
wcreg #data,accn; // write the desired accumulator
wcreg #saved_data,macsr;// restore the original macsr
)
Additionally, it is required that writes to the accumulator extension registers be performed
after the corresponding accumulators are updated. This is needed since a write to any
accumulator alters the contents of the corresponding extension register.
For more information on saving and restoring the complete EMAC programming model,
see appropriate section of the EMAC specification.
29.5.3.3.10 Write Control Register (
WCREG)
The operand (longword) data is written to the specified control register. The write alters all
32 register bits.
Command/Result Formats:
15 1211 87 43 0
Command 0x2 0x8 0x8 0x0
0x0 0x0 0x0 0x0
0x0 Rc
Result D[31:16]
D[15:0]
Figure 29-35. WCREG Command/Result Formats