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L-bus data error conditions are signalled along with the transfer acknowledge for the
access. L-bus data error conditions may occur because of privilege violations, access to
protected memory, etc. In such cases, for a read access, the ERR bit of the UDI is set, and
the DV bit in the UDI is reset at the termination of the access. For a write access, an error
public message (TCODE = 8) is transmitted (error code 0b00011).
22.5.6
Exception Sequences
The following cases are defined for sequences of the read/write protocol that differ from
those described in the above sections:
1. If the SC bit is set to start READI read/write accesses, without valid values in the
RWAD, then an L-bus address error may occur, which is handled as described above.
2. If a block access is in progress with all the cycles not yet completed, and the RWA
is written to again, (with or without modifications), then the block access is
terminated at the boundary of the nearest completed access. The resulting data is
discarded and not written to the UDI. If a new access has been programmed in the
RWA register, then that access will start once the controller has recovered.
3. When a block access is in progress with all the cycles not yet completed, writing
the SC bit to 0 in RWA register will terminate the block access and device will send
out device ready for upload/download message.
4. If a any type (single/block) of access is in progress with the cycles not yet
completed, and system reset occurs, the device will send out an error message. The
access will be terminated and the SC bit will be reset. Refer to Table 22-20.
5. If any type of (single/block) of access is requested while system is in reset, the
device will send out an error message. The access will not be started and the SC bit
will be reset.
22.5.7
Secure Mode
For details refer to Section 22.0.3.2, "Security."
22.5.8
Error Messages
22.5.8.1 Read/Write Access Error
An error message is sent out when an L-bus access error or data error on a write access
occurs. The error code within the error message indicates that an L-bus address or L-bus
data error occurred. For other error handling, see Section 22.5.5, "Error Handling." For a
list of error codes, refer to Table 22-20.
MOTOROLA
PRELIMINARY—SUBJECT TO CHANGE WITHOUT NOTICE
Chapter 22. READI Module
Read/Write Access
22-71
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