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Issue #204 June 2007
Pyxos Power
by Tom Cantrell
Start | LAN-In-the-Box |Down to the Wire | Variable interest | Hook 'Em Danno |Build it and they will come | Match point | Sources and PDF
| Timeslots | Frame time[1] | Pilot average SPI bandwidth[2] | Point average SPI bandwidth[2] |
| 2 | 1.8 ms | 175 kbps | 70 kbps |
| 4 | 3.4 ms | 190 kbps | 38 kbps |
| 6 | 4.9 ms | 195 kbps | 26 kbps |
| 8 | 6.5 ms | 198 kbps | 20 kbps |
| 10 | 8.0 ms | 200 kbps | 16 kbps |
| 12 | 9.5 ms | 201 kbps | 13 kbps |
| 14 | 11.1 ms | 202 kbps | 12 kbps |
| 16 | 12.6 ms | 203 kbps | 10 kbps |
| 18 | 14.2 ms | 203 kbps | 9.0 kbps |
| 20 | 15.7 ms | 204 kbps | 8.1 kbps |
| 22 | 17.3 ms | 204 kbps | 7.4 kbps |
| 24 | 18.8 ms | 204 kbps | 6.8 kbps |
| 26 | 20.3 ms | 205 kbps | 6.3 kbps |
| 28 | 21.9 ms | 205 kbps | 5.9 kbps |
| 30 | 23.4 ms | 205 kbps | 5.5 kbps |
| 32 | 25.0 ms | 205 kbps | 5.1 kbps |
| [1] Approximate value | |||
| [2] Sustained average rate. Peak rate may be significantly greater. | |||
| Table 1—The bandwidth and latency (i.e., frame time) specs for the Pilot and Points depends on the number of devices attached to the network. One implication is that a hosted Point may well be able to get by with a bit-banged SPI, but a Pilot probably requires a host MCU that includes a high-speed (e.g., 1 Mbps) hardware SPI | |||
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