Motorola MPC533 Reference Manual page 1005

22.5.9 Faster Read/Write Accesses with Default Attributes
Read/write access throughput may be increased by taking advantage of the default settings
of the RWA register, and truncating the least significant zero bits of the download request
message. For example, to read a word from the default memory map, with default
attributes, a download request message that selects the RWA register, and transmits the SC,
RWAD, RW fields only is sufficient. This message will contain 41 bits instead of the 94 bits
for writing the full contents of the RWA register. See Table 22-11 and Section 22.1.4,
"Partial Register Updates," for RWAR and partial register update details respectively.
The last data bit transmitted in the download request message
(TCODE 18) will always be the MSB of the register referenced
by the opcode (SC field in the case of the RWA register).
22.5.10 Throughput and Latency
Throughput analysis has been performed for various read/write access cases such as single
write, block write, single byte read, single word read, block byte read, block word read
accesses to memory-mapped locations. Data is presented for the two cases when the RWA
register is written partially and completely.
22.5.10.1 Assumptions for Throughput Analysis
• All accesses are single read accesses only.
• MCKI running at 28 MHz.
• MCKO running at 40 MHz.
• 40-MHz internal operation.
• Five clock internal L-bus access (read)
• Output signals always free (not in middle of transmission) when requested.
• One idle clock between read messages.
• No delay from tool in responding — tool keeps up with READI port.
MOTOROLA
PRELIMINARY—SUBJECT TO CHANGE WITHOUT NOTICE
NOTE
Chapter 22. READI Module
Read/Write Access
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