Motorola MPC533 Reference Manual page 1017

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.
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 RCPU is in debug mode, data trace and R/W access are allowed.
The flow chart in Figure 22-82 shows RCPU development access configuration via
READI. The modes of RCPU development access via READI are described below.
Allowed modes are also summarized in Table 22-8 of Section 24.1.1.5, "RCPU
Development Access Modes."
22.9.2.1 Enabling RCPU Development Access Via READI Signals
Reset sequencing is done by the tool to initialize the READI signals 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.
The READI module will ignore any incoming DSDI data
messages when the module is not configured for RCPU
development access.
22.9.2.2 Entering Background Debug Mode (BDM) Via READI Signals
There are three ways to enter debug mode (provided debug mode has been enabled):
1. Enter debug mode (halted state) out-of-system reset through READI module
configuration. This is displayed in Figure 22-83.
2. Enter debug mode by downloading breakpoint instructions through RCPU
development access when in non-debug (running) mode.
3. Enter debug mode if an exception or interrupt occurs.
When entering debug mode following an exception/breakpoint, the RCPU signals
VFLS[0:1] are equal to 0b11. This causes READI to send a BDM status message to the tool
indicating that the RCPU has entered debug mode and is now expecting instructions from
the READI signals.
MOTOROLA
PRELIMINARY—SUBJECT TO CHANGE WITHOUT NOTICE
NOTE
Chapter 22. READI Module
RCPU Development Access
22-85