Transfering 9-Bit serial data frames
Serial communication with 9-Bit framing (9-Bit protocol, 9 bit mode) is mainly used to identify the address byte within messages running on a RS-485 multidrop network but also on standard RS-232 connections.
On a RS-485 network the Computer (PC) usually acts as master and controls one or many clients (e.g. micro controllers). The PC working as master polls on one or more clients but always one client at a time. Once the client controller receives a request starting with it's 9-bit address it replies accordingly.
There is also often the requirement that the PC should act as slave, receive 9-bit frames, recognise its address and only then respond accordingly.
9-Bit frames are usually not supported by the standard PC's UART but simulated by the SuperCom software (Windows and Linux). Very fast response timing (low latency) by the software is essential to accomplish stable 9-bit data communication. SuperCom does provide a very realiable solution here to be used with high level languages.
The SuperCom software can be used to build master and also the client / slave side of the connection.
Many Samples (e.g. C/C++, C#, Delphi, Pascal, VB net) also included in SuperCom serial library that demonstrate this operating mode.
For example, transmitting a data packet using 9-bit addressing e.g.:
NOTE: The DEMO software found online, even when activating RS-485, are working with limited functionality, especially when it comes to response timing. The complete functionality is contained only in the licensed version.
9-Bit data communication is demonstrated by many example programs (client and server) written with C/C++, C#, Delphi, Pascal, VB net. The SuperCom Suite ships with an additional samples pack including special sample programs demonstrating 9-bit background data collection and event-driven 9-bit data capture. The event-driven working mode facilitates integration in a so-called Slave application. The data acquisition works quite independently of the GUI without blocking other processes.
The event-driven 9-bit working mode is used in many different types of projects e.g. controlling many embedded devices on a multidrop network. The event-driven 9-bit working mode is also very handy if it comes to control gaming machines using special data communication protocols (e.g. SAS Serial Protocol*).
* Slot Accounting System (SAS) protocol. A special serial data communication protocol, that is often used to query gaming machines using EIA 232 serial port connections.