Rev. 0.1 2/10

Copyright © 2010 by Silicon Laboratories

AN452

AN452

1. Overview

This specification describes in detail the Application Programmer Interface (API) for the Silicon Labs Wireless

Wireless M-Bus is a European standard for meter reading applications using the 868 MHz frequency band.

1.1. Stack Layers

Wireless M-Bus uses the 3-layer IEC model, which is a subset of the 7-layer OSI model. See Figure 1.

Figure 1. Stack Layers

The Physical Layer (PHY) is defined in EN 13757-4. The Physical Layer defines how the bits are encoded and

transmitted, the RF modem characteristics (chip rate, preamble, and synchronization word), and RF parameters

(modulation, center frequency, and frequency deviation).

the RF and modem functions. The EZRadioPRO is used in FIFO mode with the packet handler disabled. The

MbusPhy.c module provides SPI interface, encoding/decoding, block read/write, and packet handling and

manages the transceiver states.

The M-Bus Data Link Layer is implemented in the MbusLink.c module. The M-Bus Application Programming

interface consists of public functions that may be called from the Application Layer in the main thread. The

MbusLink module also implements the Data Link Layer. The Data Link Layer will format and copy data from the

application TX buffer to the MbusPhy TX buffer, adding the required headers and CRCs.

The Application layer itself is not part of the M-Bus firmware. The Application Layer defines how a wide variety of

data is to be formatted for transmission. Most meters only need to transmit one or two types of data. Adding a large

amount of code to accommodate any kind of data to the meter would add unnecessary code and cost to the meter.

If might be feasible to implement a library or a header file with an exhaustive list of data types. However, most

metering customers know exactly what kind of data they need to transmit and can refer to the standard for

formatting details. A universal reader or sniffer might implement a complete set of application data types on the PC

GUI. For these reasons, the Application Layer is implemented using example applications for a meter and reader.

PHY

EN 13757-4

Data Link

EN 60870-5-2

Application

EN 13757-3

phy

Si443x

MCU

M-Bus

app