-Data Transfer Patterns

12.7 Data Rate Control

Data Transfer Patterns

A data pattern is a sequence of letters indicating the data and unused cycles that repeat to provide the appropriate data rate. For example, the data pattern DDxx specifies a repeatable data rate of two doublewords every four cycles, with the last two cycles unused. Table 12-6 lists the maximum processor data rate for each of the possible secondary cache write cycle times, and the most efficient data pattern for each data rate.

Table 12-6 Transmit Data Rates and Patterns

In Tables 12-6 and 12-7, data patterns are specified using the letters D and x; D indicates a data cycle and x indicates an unused cycle. Figure 12-40 shows a read response in which data is provided to the processor at a rate of two doublewords every three cycles using the data pattern DDx.

Figure 12-40 Read Response, Reduced Data Rate, System Interface in Slave State

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