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Programming Model
2. The tool waits for device ready for upload/download message (TCODE 16) before
initiating next access.
To read control or status from READI tool mapped registers the following sequence would
be required
1. The tool confirms that the device is ready. The tool transmits the upload request
message (TCODE 17) which contains the target opcode.
2. When device reads data it transmits upload/download information message
(TCODE 19) containing read data. Device is now ready for next access.
Refer to Section 22.5, "Read/Write Access," for more details on read/write access protocol.
22.1.4
Partial Register Updates
Registers may be updated via the auxiliary port using the download request message with
the message containing only N (where N is less than register width) most-significant bits
of the register. In such cases the bits not transmitted will be reset to 0b0. The bits
transmitted will be aligned such that the last bit transmitted will be the most significant bit
of the register. Therefore a message size that is divisible by the input port size should be
transmitted.
22.1.5
Programming Considerations
The following programing guidelines are recommended for users of the READI features.
22.1.5.1 Program Trace Guidelines
Program trace via BTM is not supported during BDM.
For program trace synchronization to work, the ICTRL register (Refer to
Table 21.6.11)must be programmed such that show cycles will be performed for all changes
in the program flow (ISCTL field = 0b01) or the PTM bit in the READI MC register must
be set and the ISCTL field in the ICTRL register must not equal 0b11.
The user must program the ICTRL for change of flow show
cycles or the PTM bit in the READI MC register early in the
reset vector, before any branches, otherwise trace is not
guaranteed.
If BDM is enabled, the ICTRL register cannot be modified through the program and can
only be modified through RCPU development access.
To get the best performance from the system, PTM should be set to 1 and ISCTL should be
set to 0b10. It is also recommended that the USIU be programmed to ignore instruction
22-20
PRELIMINARY—SUBJECT TO CHANGE WITHOUT NOTICE
NOTE
MPC533 Reference Manual
MOTOROLA
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