Motorola MC68824 User Manual page 154

APPENDIX D
PERFORMANCE
It is necessary to understand certain aspects of the token bus controller to compute certain network
parameters such as slot time. The following describes simulations that were done to give the
user the required performance numbers. In general, the numbers given are for the worst case
situation. The simulations were run for network data rates of 10 Mbps and 5 Mbps. The numbers
given are in symbol times (bits) elapsed from the end of the end delimiter (ED) to the start of
TBC preamble and take into account the I/O sampling delays in the TBC.
System Parameters:
Address Length: 48 bits
TBC mode bits are in their default state except predefined response mode is enabled, in-ring
desired is enabled, and all statistics are enabled.
Bus Width: 16 bits
Bus Latency: one cycle
Wait States: none
Commands: none
BD and FD pools are not empty with no warning bits
Preamble: minimum length
Interrupt Status Bits: none are set
Counters: not equal to thresholds
For performance reasons, it is required that a frequency ratio of systems clock to serial clock is
greater than 1: 1.
MC68824 USER'S MANUAL MOTOROLA
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