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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
August 2006
Developer’s Manual
Reference Number: 306262-004US
735
HSS Coprocessor—Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
13.4.2
Overview of HSS Clock Configuration
The HSS clock can be configured by using the HSS API in IXP400 software releases 1.4
and later. The clock speed can be set by using the HSS API.
It is important to be aware of the jitter and frequency error on the output clock of the
HSS. The six clock values in
have been pre-defined by IXP400 software
release 1.4 to minimize jitter and PPM error. The six clock values can only be selected
by using the HSS API.
Table 238.
HSS Tx/Rx Clock Output
HSS Clock Output
Frequency
Protocol
Frame Size
(Bits)
Notes
512 KHz
GCI
32
1.536 MHz
GCI
96
1.544 MHz
1 T1
193
2.048 MHz
1 T1/E1
256
4.096 MHz
2 T1/E1
512
8.192 MHz
4 T1/E1
1,024
Notes:
1.
These clock speeds are supported using the HSS API. However, the GCI protocol is not supported by
the Intel
®
IXP400 Software.
2.
When the frequencies of 2.048, 4.096, or 8.192 MHz are used for T1, the data rate for each T1
remains at 1.544 MHz by making certain time slots within a frame unassigned and with no data. The
HSS for the IXP45X/IXP46X network processors
can be configured to discard unassigned time slots.
Table 239.
HSS Tx/Rx Clock Output Frequencies and PPM Error
HSS Tx/Rx
Frequency
Min. Frequency
(MHz)
Avg.
Frequency
(MHz)
Max.
Frequency
(MHz)
Avg. Frequency
Error
(PPM)
Notes
512 KHz
0.508855
0.512031
0.512769
-60.0096
1.536 MHz
1.515
1.536
1.55023
-60.0096
1.544 MHz
1.515
1.5439
1.55023
+60.0024
2.048 MHz
2.01998
2.0481
2.08313
-60.0096
4.096 MHz
3.92118
4.0962
4.16625
-60.0096
8.192 MHz
7.4066667
8.1925
8.3325
-60.0096
Notes:
1.
These HSS Tx/Rx clock output frequencies are based on the set-up parameters in
2.
Characterization data of the HSS Tx/Rx clock output frequency data was determined by silicon simulation.
3.
The parts-per-million (PPM) error rate is calculated using the average output frequency versus the ideal frequency.
Table 240.
HSS Tx/Rx Clock Output Frequencies and Associated Jitter Characterization
HSS Tx/Rx Clock
Output Frequency
Pj Max. (ns)
Cj Max. (ns)
Aj Max. (ns)
512 KHz
12.189
15
18.283
1.536 MHz
9.063
15
86.102
1.544 MHz
12.359
15
210.099
Note: