AN2505 Freescale Semiconductor / Motorola, AN2505 Datasheet - Page 11

• Manufacturer Part Number: AN2505
• Description: MSC8102 Asynchronous DSI Throughput
• Manufacturer: Freescale Semiconductor / Motorola

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The observed maximum throughput for the asynchronous DSI reads and writes on the MSC8102ADS are given in
Section 4. These numbers are based on the maximum frequency of the MSC8102 DSI, which is 70 MHz. Of
course, the DSI does not have to operate at that frequency. In a system in which power is a consideration, the
MSC8102 may be required to operate at a lower core and bus frequency. This section provides graphs based on
observed data that illustrate the throughput obtained when the frequency of the MSC8102 local bus is changed.
5.1 Single Read Versus Local Bus Frequency
Figure 11 illustrates the DSI throughput for a single read transaction versus the local bus frequency of the
MSC8102. The DSI operates on the basis of the local bus frequency.The maximum throughput occurs when the
local bus frequency is 70 MHz or higher. Furthermore, the throughput drops by 30 percent when the frequency is
reduced to 20 MHz.
Freescale Semiconductor
Actual Throughput Versus Frequency






System Bus Clock
Figure 11. DSI Single Read Throughput Versus MSC8102 Local Bus Frequency
HWBS0/PWE0

HBCS/CS3
Address

Figure 10. Asynchronous Broadcast Host DMA Write
MSC8102 Asynchronous DSI Throughput, Rev. 1

8102 Local Bus Frequency (MHz)



Actual Throughput Versus Frequency



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