Bacnet Status Indicators - Zener MSC-3 Instruction Manual

MSC-3 Start Up
• G167 Terminator: If necessary each MSC-3 is capable of terminating the EIA-485 network.
Setting this parameter to ENABLED will terminate the line.
• G169 Serial No.: Each BACnet device has a name, which is required to be unique. To ensure
that there are no duplicated names, the MSC-3 serial number is used as part of the device object
name.
7. Connect the MSC3 to the BACnet network.

BACnet Status Indicators

Several displays are available in the service menu to check network activity and state.
MODBUS RTU (EIA/RS-485)
The MSC-3 MODBUS RTU interface implements MODBUS as described in Modbus-IDA.ORG
documents "MODBUS over Serial Line specification and implementation guide V1.02" and
"MODBUS Application Protocol Specification V1.1b".
MODBUS Memory Model
The MODBUS memory model for the MSC-3 has separate blocks for Discrete Inputs, Coils, Input
registers and holding registers. See the MODBUS appendix for details on addresses and sizes of each
block.
Supported MODBUS Function Codes
• Function Code 01: Read Coils
• Function Code 02: Read Discrete Inputs
• Function Code 03: Read Holding Registers
• Function Code 04: Read Input Registers
• Function Code 05: Write Single Coil
• Function Code 06: Write Single Register
• Function Code 07: Read Exception Status
• Function Code 08: Diagnostics, Sub Codes 0,2,10...18,20
• Function Code 15: Write Multiple Coils
• Function Code 16: Write Multiple Holding Registers
• Function code 43: Read device Identification, Sub Code 14
See the MODBUS appendix for details on function codes and sub codes.
MODBUS Exceptions
Except for broadcast messages, when a master device sends a query to the MSC-3 drive it expects a
normal response. One of four possible events can occur from the master's query:
1. If the MSC-3 receives the query without a communication error, and can handle the query normally,
it returns a normal response.
2. If the MSC-3 does not receive the query due to a communication error, no response is returned.
3. If the MSC-3 receives the query, but detects a communication error (parity or CRC), no response is
returned..
4. If the MSC-3 receives the query without a communication error, but cannot handle it (for example,
if the request is to read a non-existent coil or register), the MSC-3 will return an exception response
informing the master of the nature of the error.
See the MODBUS appendix for details on function codes and sub codes.
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