INTERBUS scanning time

Introduction

The INTERBUS scanning time is the input/output update time. It is dependent on the number of and words exchanged cyclically on the bus.

Calculation of time

The scanning time is calculated by the following formula:

Equation parameters

Parameter	Meaning
t	Scanning time
n	Number of DP and PCP bytes to transmit
m	Number of modules connected to the RB (including station headers)
tb	Transmission time for one bit (0.002 ms to 500 Kbits/s)
ts	Constant of IBS software interscan time (0.9 ms)
tp	Cable propagation time (0.016ms/Km)

Graph 1

The following figure presents the IBS scanning time graph.

PCP

Peripherals Communication Protocol: communication protocol for peripherals (layer 2 of the OSI model). This fragments and reconstitutes messages during transmission. It makes available all the services needed for connection and disconnection, and the data transmission services.

IBS

INTERBUS: this bus uses the master-slave process. The master subscriber module manages and coordinates bus access. It transmits data to all the subscribers and receives data from them.