FANUC Robotics America GFK-1535A - Manual (Page 47)

GFK-1535A Chapter 3 Operation 3-7
3
Genius Bus Scan Time
The Genius bus scan time is dependent on the number of devices and amount of
data traffic on the bus. The bus scan time may vary from 3-400ms, but 20-30ms is
typical. It cannot be less than 3ms.
The Genius bus scan time contribution for the NIU depends on its I/O data usage.
The table below shows the scan time contribution, at each baud rate, for stations
with a total of 16, 32, 64, 128, and 256 bytes, when the NIU receives outputs from
only one bus controller at a time.
To find the exact scan time contribution for the NIU, follow the procedure below.
Total Amount of Input Contribution time in ms at each baud rate
and Output Data 153.6 Kb std 153.6 Kb ext 76.8 Kb 38.4 Kb
16 bytes 2.09 2.16 3.83 7.16
32 bytes 3.24 3.31 6.12 11.74
64 bytes 5.52 5.60 10.69 20.89
128 bytes 10.10 10.17 19.85 39.20
256 bytes (fully-loaded) 19.25 19.32 38.15 75.80
Procedure for Estimating Bus Scan Time
1. Find the total number of input bytes and output bytes. (Each analog
channels is 2 bytes. Each eight discrete points are one byte).
number of input bytes = ________
number of output bytes = ________
total bytes = ________
2. With this total, calculate a scan time contribution using the formula below
that corresponds to the Genius bus baud rate.
Formula for 153.6 Kbaud Standard:
0.943ms + (0.0715 x total bytes) = ________ ms
Formula for 153.6 Kbaud Extended:
1.015ms + (0.0715 x total bytes) = ________ ms
Formula for 76.8 Kbaud:
1.538ms + (0.143 x total bytes) = ________ ms
Formula for 38.4 Kbaud:
2.583ms + (0.286 x total bytes) = ________ ms