Motorola MPC533 Reference Manual page 1002

Read/Write Access
22.5.4.2 Read Operation
For a read access to internal READI registers, the following sequence of operations need
to be performed via the auxiliary port:
1. The tool confirms that the device is ready before transmitting upload request public
message (TCODE = 17).
2. The upload request public message contains:
a) TCODE(17)
b) Access opcode, which specifies the register where data needs to be read from,
(for example, access opcode 0x14 indicates that DTA1 register is the target
register).
3. The upload/download information public message (TCODE=19) is transmitted to
the tool along with the data read from the targeted register indicating that the device
is ready for next access.
22.5.5 Error Handling
The READI module handles the various error conditions in the manner shown in the
following sections.
22.5.5.1 Access Alignment
The READI module will force address alignment based on the word size field (SZ) value.
If the SZ field indicates word (32-bit) access, the least significant two bits of the read/write
address field (RWAD) are ignored. If the SZ field indicates half-word (16-bit) access, the
least significant bit of the read/write address field (RWAD) is ignored.
22.5.5.2 L-Bus Address Error
An address error occurs on the L-bus when the address phase of a cycle is not completed
normally. This could occur because of address not being valid or the address map not being
valid. In such cases:
1. The access is terminated without retrying.
2. The SC bit of the RWA is reset. Block accesses do not continue.
3. The error message (TCODE = 8) is transmitted (error code 0b00011). Refer to
Table 22-20.
22.5.5.3 L-Bus Data Error
L-bus data error is signalled due to:
• L-bus data phase error.
• U-bus address phase error (for a L-bus to U-bus cycle).
• U-bus data phase error (for a L-bus to U-bus cycle).
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