Motorola MPC533 Reference Manual page 1016

RCPU Development Access
BDM status message (with BDM status field equal to 0b1) is sent when the RCPU is in
debug mode and the device is ready to receive debug mode messages.
BDM status message (with BDM status field equal to 0b0) is sent out when the device exits
BDM mode and RCPU is in normal operating mode.
The BDM status message has the following format:
[1 bit]
[6 bits]
TCODE (58)
BDM Status
Length = 7 bits
Figure 22-80. BDM Status Message Format
22.9.1.4 Error Message (Invalid Message)
An error message is sent out when an invalid message is received by READI. The error
code within the error message indicates that an invalid TCODE was detected in the
auxiliary input messages by the signal input formatter. Refer to Table 22-20.
The error message has the following format:
[6 bits] [5 bits]
TCODE (8) Error Code (0b00100)
Length = 11 bits
Figure 22-81. Error Message (Invalid Message) Format
22.9.2 RCPU Development Access Operation
The RCPU development access can be achieved either via the READI signals or the BDM
signals.
To enable RCPU development access via the READI signals, the tool has to configure the
DC register during the READI reset (RSTI). Once the READI module takes the control of
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 signals, 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 signals.
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.
22-84 MPC533 Reference Manual MOTOROLA
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