29-11
MPC8260 PowerQUICC II UserÕs Manual
MOTOROLA
Part IV. Communications Processor Module
29.3.3.2 Determining the Number of Slots in a Scheduling Table
The number of time slots in a scheduling table is determined by the channel with the
minimum bit rate; see equation B. The minimum bit rate is achieved when the channel
reschedules only once in a whole table scan. (The maximum schedule advance allowed is
equal to number_of_slots-1.) For example, if the line rate is 155.52 Mbps, the minimum bit
rate is 32 kbps and the CPS is 4, then, according to equation B, the number of slots should
be 1,216.
For the above example, 32 kbps = 155.52 Mbps/((1216-1)
´
4).
Use equations (A) and (B) to obtain the maximum and minimum bit rates of a scheduling
table. For example, given a line rate = 155.52 Mbps, number_of_slots = 1025, and CPS = 8:
29.3.4 Determining the Time-Slot Scheduling Rate of a Channel
The time-slot scheduling rate of each ATM channel is deÞned by equation C. The resulting
number of APC slots is written in either TCT[PCR], TCTE[SCR] or TCTE[MCR],
depending on the trafÞc type.
29.3.5 ATM TrafÞc Type
The APC uses the cell rate pacing parameters (PCR, SCR, and MCR) to generate CBR,
VBR, ABR, UBR+, and UBR trafÞc. The user determines the kind of trafÞc that is
generated per VC by writing to TCT[ATT] (ATM trafÞc type); see Section 29.10.2.3,
ÒTransmit Connection Table (TCT).Ó
29.3.5.1 Peak Cell Rate TrafÞc Type
When the peak cell rate trafÞc type is selected, the APC schedules channels to transmit
according to the PCR and PCR_FRACTION trafÞc parameters. Other trafÞc parameters do
not apply to this trafÞc type.
29.3.5.2 Determining the PCR TrafÞc Type Parameters
Suppose a VC uses 15.66 Mbps of the total 155.52 Mbps and CPS = 8. Equation C yields:
Min bit rate =
(B)
(number_of_slots
- 1)
´
cells per slot
line rate
Max bit rate = (155.52 Mbps)/8 = 19.44 Mbps
Min bit rate = (155.52 Mbps)/(1024
´
8) = 18.98 kbps.
Rate [slots] =
(C)
VC rate [bps]
´
cells per slot
line rate [bps]
PCR [slots] = (155.52 Mbps)/(15.66 Mbps
´
8) = 1.241
Summary of Contents for MPC8260 PowerQUICC II
Page 1: ...MPC8260UM D 4 1999 Rev 0 MPC8260 PowerQUICC II UserÕs Manual ª ª ...
Page 66: ...lxvi MPC8260 PowerQUICC II UserÕs Manual MOTOROLA ...
Page 88: ...1 18 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA Part I Overview ...
Page 120: ...2 32 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA Part I Overview ...
Page 138: ...Part II iv MPC8260 PowerQUICC II UserÕs Manual MOTOROLA Part II Configuration and Reset ...
Page 184: ...4 46 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA Part II ConÞguration and Reset ...
Page 202: ...Part III vi MPC8260 PowerQUICC II UserÕs Manual MOTOROLA Part III The Hardware Interface ...
Page 266: ...8 34 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA Part III The Hardware Interface ...
Page 382: ...10 106 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA Part III The Hardware Interface ...
Page 392: ...11 10 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA Part III The Hardware Interface ...
Page 430: ...Part IV viii MOTOROLA Part IV Communications Processor Module ...
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Page 980: ...A 4 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA Appendixes ...
Page 1002: ...Index 22 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA INDEX ...
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