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MPC565/MPC566 Reference Manual
MOTOROLA
RCPU Development Access
RCPU development access, the protocol for transmission of development serial data in
(DSDI) and out (DSDO) is performed through the IEEE-ISTO 5001-1999 compliant
vendor-defined messages.
After enabling RCPU development access via the READI pins, the READI module can
enable debug mode and enter debug mode. When debug mode is enabled and entered,
READI sends a BDM status message (BDM status field equal to 0b1) to the development
tool indicating that the RCPU has entered debug mode and is now expecting instructions
from the READI pins.
The development tool then uses the DSDI Data Message to send in the serial transmission
data to READI. Data is transmitted to the tool using the DSDO data message.
This process continues until the RCPU exits debug mode and READI sends the BDM status
message (BDM status field equal to 0b0) indicating debug mode exit.
NOTE
Only after the DSDO data message is sent out should another
DSDI data message be sent in.
Synchronous self-clocked mode is selected by READI for RCPU development access. In
this mode, the internal transmission between READI and the USIU is performed at system
frequency.
When the RCPU is in debug mode, program trace is not allowed. If program trace is
enabled, a program trace synchronization message is generated when debug mode exits.
When the RCPUisindebug mode,datatrace andR/W access are allowed.
The flow chart in
Figure 23-80 shows RCPU development access configuration via
READI. The modes of RCPU development access via READI are described below.
23.10.2.1 Enabling RCPU Development Access Via READI Pins
Reset sequencing is done by the tool to initialize the READI pins and registers by asserting
RSTI (the device sends out the device ID message after the RSTI negation). System reset
is held by the tool until the READI module is reset and initialized with desired RCPU
development access setting.
For RCPU development access to be enabled via the READI pins, the tool has to configure
the DC register (DPA field equal to 0b1) after the negation of RSTI, but before the negation
of system reset. System reset should only be negated at least 16 system clocks after the DC
register has been configured.
If the DC register is not configured such that READI module has control of the RCPU
development access signals before the negation of the system reset, then RCPU