Development Support
18-40
MPC801 USER’S MANUAL
MOTOROLA
18
For large blocks of data, this sequence can take a significant amount of time to complete.
But, using the fast download procedure of the debug port reduces this time because the
need to transfer the instructions in the debug port loop is eliminated. The only transactions
needed are those used to transfer the data to be placed in the system memory.
Figures 18-13 and 18-14 illustrate the benefit of using the fast download procedure.
Figure 18-13. Slow Download Procedure Loop
Figure 18-14. Fast Download Procedure Loop
The sequence of the instructions used in the fast download procedure is illustrated in
Figure 18-12, with RX = r31 and RY = r30. This sequence is repeated infinitely until the end
download procedure command is issued to the debug port. The internal general-purpose
register 31 is used for temporary storage of the data value. Before beginning the fast
download procedure by the start download procedure command, the value of the first
memory block address -4 must be written into the general-purpose register 30. To end the
download procedure, an end download procedure command should be issued to the debug
port and then an additional data transaction should be sent by the development tool. This
data word will not be placed into the system memory, but it is needed to stop the procedure.
18.4 THE SOFTWARE MONITOR DEBUGGER
When in debug mode disable, a software monitor debugger can use all of the development
support features defined in the core. When debug mode is disabled, all events result in
regular interrupt handling (the processor resumes execution in the corresponding interrupt
handler). The ICR and DER only influence the assertion and negation of the freeze signal.
EXTERNAL
TRANSACTION
MFSPR
DATA
STWU
INTERNAL
ACTIVITY
EXTERNAL
TRANSACTION
DATA
INTERNAL
ACTIVITY