HIMA HIMax, Системное руководство

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HIMax System 3 Product Description
HI 801 001 E Rev. 4.01 Page 27 of 122
1 800 m
0 2
17 400 m
15 1
7 800 m
7 800 m
Rack with I/O Modules
Rack with Processor Modules
Ethernet Copper Cable Converter Copper Cable <-> Fiber Op-
tic Cable
Fiber Optic Cable
Figure 6: Maximum distance between processor modules with latency default value
ƒ The delay time between rack 0 and rack 1 is composed of the delay due to both
converters (1 µs) and the delay due to the fiber optic cable (max. 10 µs - 1 µs). The
following formula applies to the delay due to the fiber optic cable and its length:
9 µs
≥ length * 5 µs / km, i.e., length ≤ 1 800 m
ƒ The delay time between left rack with I/O modules (in the example rack ID 2) and the
right rack with processor modules (rack ID 1) is composed of:
-
The delay on the distance between the rack 0 and rack 1 (see above) and
-
the delay on the distance between base plate 0 and base plate 2, on the left. The
maximum delay must be 50 µs - 10 µs = 40 µs.
It is composed of the delay due to both converters (1 µs) and the delay due to the
fiber optic cable (max. 39 µs). The following formula applies to the delay due to the
fiber optic cable and its length:
39 µs
≥ length * 5 µs / km, i.e., length ≤ 7 800 m
The same formula applies to the length of the fiber optic cable between rack 1 and rack 15,
the maximum length of the fiber optic cable is also 7 800 m.
3.2.3.2 Calculating a User-Specific Maximum System Bus Latency
The following factors must be taken into account when calculating the maximum system
bus latency:
ƒ The latency of additional network components, if used
ƒ 65 µs must be added for each rack.
To determine the maximum system bus latency consider all the rack connections from the
processor module to other racks.
The greatest value, obtained from the latency of all network components between the racks
with a processor module and the considered rack, corresponds to the minimum value of the
maximum latency.
Figure 7 shows the connection between two base plates, rack A and rack B through a fiber
optic cable path.