![]() ![]() ![]() The Five Wire Toolset meets this embedded engineering challenge with high-speed logic sensing, analyzer, pattern generators, and an interface channel. Five-in-One Testing: The Five Wire Toolset Hence the need for a debug solution that complements the oscilloscope, as well as a tool that has additional real-time MCU debugging capability. This problem is only compounded as the complexity of the system increases. Software simulation is another inexpensive alternative, but it does not perform at the speed of modern MCUs. Thus, they are often more suitable for lower-resolution debugging tasks. However, they display signals in their digital form, and therefore provide only an indirect view of how firmware responds to different inputs. This also allows them to interface with larger screens that make it easier to visualize long sequences of digital events. Logic analyzers support greater channel counts and have come down in price thanks to PC technology. On the other end of the debug tool spectrum, there is the full-blown Logic Analyzer. In a real-time debugging context like the I 2C environment described above, the oscilloscope can quickly become awkward because of the primary trigger that requires a repetitive signal. Once a bus collision is detected, the slave goes Idle and waits to be addressed again. ![]() If the SDA line was low (NACK), the next transmit data must be loaded into the SSPBUF register.Ī bus collision occurs any time the SDA line is sampled low, while it is outputting and expected high state. The slave idles and waits for the next Start bit occurrence. If the NACK is high, the data transfer is complete. The NACK pulse from the master latches on the rising edge of the 9th SCL input pulse. Then, the SCL pin is released, and the eight data bits are shifted out coincidental to the SCL input's falling edge, ensuring a valid SDA signal during the SCL high time. The transmit data is loaded into the slave register. With this stretched clock signal, the master is unable to assert another clock pulse until the slave prepares to transmit data. Following ACK, slave hardware lowers the SCL pin, starting the clock stretching period. The received address is loaded, and the slave sends an ACK pulse on the 9th bit. Typical I 2C Slave Transmission.įor a slave transmission, a masters wants to read data from the slave and sends a Start condition (S). ![]() The important protocol communication requirements are the occurrence of the Start, Stop, ACK, and NACK signals in relation to the SDA and SCL levels (Figure 1).įigure 1. In an I 2C protocol environment, there are master and slave devices. Elongated I 2C communication streams directly challenge oscilloscopes capability of measuring activities. In a real-world application, mid-range MCU devices have a Master Synchronous Serial Port (MSSP) modules to implement either the I 2C communication protocols. Today’s MCU has a significant number of pins, busses, and I/O, that require a high-channel-count measurement system with sufficient memory for real-time debugging.Įmbedded system testing includes the examination of baud rate, wait time, and output level status. The oscilloscope faithfully captures repetitive analog signals as well as the repetitive MCU I/O digital signals, but the MCU’s capabilities of extended timing and irregular digital signals pose sophisticated timing challenges. The oscilloscope is the most popular and available MCU debug tool for the embedded developer. ![]()
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