Do you need a protocol analyser? When do you need a protocol analyser? What about other similar devices? These days there are a variety of devices that perform functions similar to a protocol analyser, or that perform some of the functions of a protocol analyser. I am talking about oscilloscopes and logic analysers.
Oscilloscopes are designed primarily for displaying the actual voltages and waveforms of signals. They usually have a limited number of channels. The connectors tend to be general purpose clips that can attach to all sorts of wires and pins. They are available as a stand-alone device, or as a piece of hardware that requires a computer for data storage and display.
Logic analysers are designed primarily for capturing and displaying many digital signals. The actual voltages are not shown, only whether a signal was high (e.g. above 2.0 V) or low (e.g. below 0.8 V). The relative timing of signals is shown (e.g. one signal went high 1ms before another signal went high), which can help with the debugging of timing issues. They often support a large number of channels. Their connectors also tend to be general purpose clips. They are also available as a stand-alone device, or as a piece of hardware that requires a computer for data storage and display.
When you need to know what is being communicated between a smart card and another device or system (for purposes of development, troubleshooting, quality control, or training), a protocol analyser is probably the tool to use. It captures the signals, analyses them according to a pre-defined protocol, and displays the data and the analysis in a meaningful way.
Protocol analysers focus on analysing the signals according to a standard protocol such as USB, ISO-7816, TCP/IP, etc. and displaying the results. Some can also generate signals, taking on the role of a node in the communication link or the network. Their connectors are specific to the supported protocol(s). They are available as a stand-alone device, or as a piece of hardware that requires a computer for data storage and display. Examples of modern protocol analysers are the MiniMove from Comprion, and the CardScope from Prism.
The data captured by a protocol analyser is often displayed as a sequence of hexadecimal digits, with the interpretation (structural element, meaning, etc.) displayed alongside the data, as shown in figure 1.
Figure 1. Interpretation of data by CardScope
In the case of smart cards (credit cards, SIM cards, identity cards, etc.), a protocol analyser is useful for:
- Development and debugging of hardware interfaces
- Development and debugging of smart card software
- Development and debugging of applications and back-end systems that communicate with smart cards
- Quality control of cards
- Quality control of devices that use smart cards
- Educating engineers about smart card protocols
Use a protocol analyser to capture, display and interpret the data on a digital communications channel. Use an oscilloscope to capture and display the exact voltages of signals in an analogue or a digital circuit. Use a logic analyser to capture and display the digital signals in a digital system.