SA Bus Rules and Specifications - BCPro - LIT-12011908 - General System Information - BCPro System - 4.0

MS/TP Communications Bus for the BCPro System Technical Bulletin

Product name
BCPro System
Document type
Technical Bulletin
Document number
Revision date

The SA bus connects CH-PCXs , VSDs, and NS-Series network sensors to CH-PC controllers. Figure 1 shows three SA bus examples. Table 1 provide SA bus rules and specifications.

Table 1. SA Bus Rules




Each bus supervisor supports one SA Bus (and each SA Bus is a single segment).

Number of Devices Supported on the SA Bus

An SA Bus supports up to 10 devices. The SA bus supervisor provides power for all subordinate devices connected to the SA bus, including up to four NS network sensors. CH-PCXs connected to the SA bus are not powered by the bus supervisor.

SA Buses do not support repeaters.

Cable Length

365 m (1,200 ft) maximum bus length

152 m (500 ft) maximum distance between an NS network sensor and the bus supervisor ( C4-CGMs, C4-CVMs, CH-PCG or CH-PCV supplying power to the sensor) using bus cable connected to the SA Bus screw terminal blocks

30 m (100 ft) maximum length for network sensors using bus cables connected to the RJ-Style modular jack (6-Pin SA Bus Port)

366 m (1,200 ft) maximum bus length

Recommended Cable Type

Screw Terminal Connections: 22 AWG Stranded 4-wire, 2-Twisted Pairs, Shielded Cable for screw terminals.

Modular Jack Connections: 6-Pin RJ-Style Modular Connectors with 24 or 26 AWG Solid 6-Wire, 3 Twisted-Pairs

EOL Termination

Each SA bus supervisor has integral (fixed ON) EOL termination, which typically provides sufficient EOL termination on an SA bus. Long SA bus runs or persistent communication problems on an SA bus may require EOL termination at the last device on the SA bus (in addition to the integral EOL termination at the SA bus supervisor).

Mixing Device Types

Do not mix RJ-style modular (phone) jack devices and screw terminal devices on the SA bus.

Note: The recommended cable types provide the best bus performance. See MS/TP Bus Cable Recommendations for information on alternative cable types.