HIMA HIMax - Page 32

3 Product Description HIMax System
HI 801 001 E Rev. 4.01 Page 32 of 122
Explanation:
2*t
Cu
2 copper cable between racks 8, 7 and switch A, switch A and rack 0
2*t
Switch
Delay due to switches A and B
n
Racks
Number of base plates, here 16
(n
Racks
-1)*t
Rack
Latency for the following racks:
 Rack 15 itself
 12 racks (1…12) connected to switch A
 One rack (13) connected to switch B
 One rack (14) connected to switch C
In this example, at least 1073 µs must be used for Maximum System Bus Latency [µs].
If this example includes a communication module inserted in rack 8, the following
considerations should be made:
 The maximum latency allowed between processor and communication modules is
305 µs in accordance with
Table 8.
 The latency between rack 0 and rack 8 is calculated as follows:
t
Latency
= 3*t
Cu
+ t
Switch
+ (n
Racks
- 1)*t
Rack
+ 3*t
Message
= 3*0.667 µs + 5 µs + 15*65 µs +
3*6.592 µs =1001.776 µs
Explanation:
3*t
Cu
3 copper cables between racks 8, 7, switch A and rack 0
t
Switch
Delay due to switch A
n
Racks
Number of base plates, here 16
(n
Racks
-1)*t
Rack
Latency for the following racks:
 12 racks (1…12) connected to switch A, including rack 8 itself
 One rack (13) connected to switch B
 Two racks (14, 15) connected to switch C
Result: The resulting maximum latency of 1001.776 µs is significantly greater than the
maximum allowed latency of 305 µs. For this reason, the communication module must not
be inserted in rack 8!