![]() Upon the reception of a full character, the ARM7 program is notified, which then can directly fetch the received data from the HET. In this case, a total of nine samples are taken after the start bit high-to-low transition was detected. Then, all other bits are read one bit period spaced apart from each other.įor this process to work, a fine time resolution is needed to minimize the offset error introduced due to the start bit detection principle.įigure 3 shows the time diagram of an example UART reception. Which is in the middle of its bit period. The value of the first data bit is then determined 1.5 bit periods after the start bit was detected, This is necessary because the incoming data is asynchronous to the HET timing. With a frequency higher than the baud rate until a zero logic level (start bit) is detected. The operational principle is that the HET UART is polling the receive signal line The entire UART data stream is output to an HET device's HET I/O pin in the background.įor the reception process, the incoming UART data stream delivered to an HET device I/O pin is decoded. That matches the UART bit timing and become active at the beginning of the following LR cycle.įor the given example, a total of 10 transitions are needed and preloaded. These transitions are preloaded into the HET pin logic in advance of the next LR cycle Using multiple LR cycles to achieve perfect hardware-generated timing.įor the transmission process, the ARM7 passes the data it wishes to transmit to the HET program.įigure 2 shows an example UART transmission.Ĭhanges to the output signal line are required only at the end of each bit period. The HET UART program processes the incoming and outgoing data streams bit by bit When the HET rolls over to the first instruction, it waits for the LR clock to restart program execution, ensuring synchronized timing. The time for a loop to execute is referred to as a loop resolution (LR) clock cycle. The HET operational principle lies in loop-oriented program execution. With independent background transmission and reception.įurthermore, interrupts are provided, allowing for an event-oriented application program flow.Ī conceptual overview of the interaction of the different components is shown in Figure 1. Using a small piece of software, designers can implement hardware UART module-like functionality The HET can be used to implement complex, timed I/O operations, such as multiple UART interfaces. The TMS470 HET peripheral is a complex, high-performance RISC coprocessor that operates independent of the main ARM7. With interrupt capability and zero ARM7 CPU overhead. TMS470 ARM7-based microcontroller at zero cost?ĭesigners can use the high-end timer (HET) peripheral found on all Texas Instruments ARM7-based,ģ2-bit TMS470 microcontrollers to implement additional, full-duplex high-speed UART interfaces ![]() How can you add extra hardware UARTs to a 32bit
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