Version 1 ColdFire Debug (CF1_DEBUG)
MCF51CN128 Reference Manual
,
Rev. 6
20-54
Freescale Semiconductor
3. The host reads the channel status using a READ_XCSR_BYTE command.
4. If XCSR[CSTAT] is 000
then the status is okay; proceed
else
Halt the CPU using a BDM BACKGROUND command
Repeat steps 1,2,3
If XCSR[CSTAT] is 000, then proceed, else reset the device
shows a SYNC command aborting a READ_MEM.B. After the command is aborted, a new
command could be issued by the host.
NOTE
signal timing is not drawn to scale.
Figure 20-22. ACK Abort Procedure at the Command Level
a shows a conflict between the ACK pulse and the sync request pulse. This conflict could
occur if a pod device is connected to the target BKGD pin and the target is already executing a BDC
command. Consider that the target CPU is executing a pending BDC command at the exact moment the
pod is being connected to the BKGD pin. In this case, an ACK pulse is issued at the same time as the SYNC
command. In this case there is an electrical conflict between the ACK speedup pulse and the sync pulse.
Because this is not a probable situation, the protocol does not prevent this conflict from happening.
READ_MEM.B
READ_XCSR_BYTE
BKGD PIN
ADDRESS[23-0]
HOST TARGET
BDC DECODES
READ_MEM.B CMD
IS ABORTED BY THE SYNC REQUEST
NEW BDC COMMAND
AND CPU TRYS TO EXECUTE
THE READ_MEM.B CMD
HOST TARGET
HOST TARGET
SYNC RESPONSE
FROM THE TARGET
NEW BDC COMMAND
(NOT TO SCALE)
(NOT TO SCALE)
