Frequently asked questions (FAQ)

What is a BIM?

A BIM (Bus Interface Module) is a module designed to be built into a target device. It contains the entire circuit required for KNX bus communication over the twisted pair medium and provides a power supply (5 V 10 mA / 20 V 5 mA) to an external hardware circuit.

How can I develop a BIM M 13.. application program?

All you need is the development tool package available from our approved distributions partners. With the development tool package you are able to create a complete BIM M 13.. application program.

It contains:

  • Evaluation board with complete BIM functionality

  • Renesas debugger to connect your PC to the EVB for On-Chip-Debugging

  • IAR Embedded Workbench (code size limited version, but enough for BIM M 130 and BIM M 131 application programs)

  • BIM Tools (free of charge), with integrated wizard to create an IAR EWB project for BIM M 13..


What microcontroller is used on the BIM M 13..?

The BIM M 13.. bus interface modules are based on the Renesas 78K0/KE2 microcontroller family. All three microcontrollers have identical hardware, they only differ in RAM and flash memory space.  The following devices are in use:

  • BIM M 130 and BIM M 135: F0534

  • BIM M 131: F0535

  • BIM M 132: F0537


What is the used programming language for BIM M 13..?

BIM M 13.. application programs are developed with the IAR Embedded Workbench in C language.

What shall I do to send a telegram on the KNX bus with a BIM M 13..?

Sending and receiving bus telegrams is done thanks to the build in communication stack embedded the BIM M 13.. operating system. The communication at application program level is done via communication objects.
To send a telegram the application program (written by the customer) just calls the API function from the operating system that reads the data from the communication object set by the application program and sends a corresponding telegram to the bus.
If a telegram is received the operating system copies the transferred payload data to the corresponding communication object of the application program that cyclically checks with another API function, what objects are updated.

Do I need an external power supply?

For normal operation mode no power supply is needed. Normally the BIM and external hardware is powered via the KNX bus.

How can I program my BIM with my own developed application?

The BIMs already contain at delivery state the operating system. Therefore it is possible to program an application program via the KNX bus. An alternative way of programming the BIMs is to use the Renesas Flash Programmer PG-FP5.

How many communication objects are possible?

The used System 2.5 operating system supports up to 254 communication objects.

How can I create an ETS database entry?

For that part, the KNX Manufacturer Tool shall be used. For further information please refer to the KNX association (http://www.knx.org).

Is there a way to reduce the consumption of the TP-UART 2 (1.8 mA with 3.3 V and V 20 deactivated)?

1.8 mA is the maximum current consumption according to the specification in normal mode. This is the supply current of the analog and digital part of TP-UART 2. It is unfortunately not possible to reduce that value.

Sometimes during bus voltage power up VCC (3.3 V/5 V) does not ramp up too. VCC remains to a lower level. What is the reason for that?

First it has to be ensured that the layout guidelines described in the technical documentation are applied.
During ramp up of VCC current IVCC shall not exceed 50 mA. IVCC during ramp up has to be measured. Reasons for an excessive IVCC current during that phase could be undefined states of controller inputs being not connected to defined levels or other transient states of the peripheral circuits.

We have noticed that the layout described in the technical documentation and the layout of the evaluation board are not exactly the same. Which one has to be applied?

It should be always tried to get as close as possible to the one in the technical documentation.

Where can we get a suitable crystal for TP-UART 2?

A suitable crystal is available from Fa. Jauch
Order-Information: Q4.91520-SMU3-16-50/50-TR-LF


Sometimes TP-UART 2 can send data to KNX data bus, sometimes not. The conditions do not change. We also cannot explain why.

The timing and frame of the data signals have to be checked.
It should be checked if the electrical characteristics of the PC-interface are o.k. and that it fulfills all requirements such as input impedance, signal levels, driver capabilities, etc., as stated in the TP-UART 2 technical documentation.

The TP-UART2 always responses on commands with an un-defined 0x47

If the TP-UART 2 receives faulty bytes it will answer with 0x47 (receive-error).
The timing and frame of the data signals have to be checked.
It should be checked if the electrical characteristics of the PC-interface are o.k. and that it fulfills all requirements such as input impedance, signal levels, driver capabilities, etc., as stated in the TP-UART2 data sheet.