AN2505 Freescale Semiconductor / Motorola, AN2505 Datasheet - Page 14

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

Summary
6
The throughput for the MSC8102 DSI asynchronous 64-bit mode is obtained by examining the signals for single
core reads/writes, host DMA reads/writes, broadcast single core writes, and broadcast host DMA writes:
The numbers provided in this application note are for one MSC8102 operating in asynchronous mode. The effects
of capacitive loading when multiple MSC8102 devices are present lowers the throughput. It is assumed that other
internal resources sharing the local bus are not in use on the MSC8102. If these modules are used, they require
access to the local bus, adversely affecting DSI performance numbers.
The MSC8102 supports an extremely fast synchronous mode of operation, which accommodates bursting. In
synchronous mode, the throughput of the MSC8102 DSI peripheral increases significantly. If the application
requires more throughput than is indicated in this application note, synchronous DSI mode should be implemented.
14
Summary
•
•
•








Single reads and writes have much lower performance numbers than the host DMA throughput results.
The throughput numbers suggest that the MSC8101 core or host processor should use only single
reads/writes when accessing a DSI register or very few memory addresses due to the lower
performance.
Since the throughput numbers are larger for host DMA reads and writes, it makes sense to use the
DMA controller for reading and writing large amounts of data from the DSI.
Broadcasting data in single transfers or host DMA transfers is much faster than not broadcasting.
Therefore, it is important to broadcast data to the MSC8102 devices as much as possible. If there is
only one MSC8102 in the system, broadcasting should be used all the time for maximum DSI
performance.
Figure 14. DSI Host DMA Write Throughput Versus MSC8102 Local Bus Frequency


MSC8102 Asynchronous DSI Throughput, Rev. 1

8102 Local Bus Frequency (MHz)




Freescale Semiconductor