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TL16C754C: Interface forum

MASAHIRO YANO
Prodigy 10 points
Part Number: TL16C754C

Tool/software:

UART-ICのデータシートについて質問があります:TL16CP754C。 TL16CP754Cデータシートのトップページに「3.3V動作用の32MHz発振器入力クロック(2Mbps)」と記載されています。 これは、動作電圧3.3Vで使用すると、32MHzの発振器入力で最大2Mbpsの通信速度が使用できるということですか? 現在、私は3.3V電源でICを実行しており、24.576MHzの発振器出力はXTAL1ピンに接続されています。 このICは使用できますか?

Sorry. The previous question may have been forwarded in Japanese, so I will resend it in English.

I have a question about the datasheet for the UART-IC: TL16CP754C. On the top page of the TL16CP754C datasheet, there is a statement that says, "32-MHz Oscillator Input Clock (2 Mbps) for 3.3-V Operation." Does this mean that when used with an operating voltage of 3.3V, a 32 MHz oscillator input can be used for communication rates of up to 2 Mbps? Currently, I am running the IC on a 3.3V power supply, and the 24.576 MHz oscillator output is connected to the XTAL1 pin. Is this acceptable for using this IC?

  • 0
    Guru 316690 points

    The maximum input clock rate depends on the supply voltage. At 3.3 V, you can use 32 MHz or less.

  • 0 in reply to Clemens Ladisch
    Prodigy 10 points

    Thank you for your reply. I'm sorry, but I'd like to ask a few more questions related to that. As I explained earlier, I'm currently operating at 3.3V and directly connecting the 24.576MHz oscillator output to the XTAL1 pin. There seem to be no problems with the waveform, both in terms of voltage and shape. Since I'm communicating with the other end at a relatively slow rate of 9600bps, the divisor value is set to exactly "160". However, the data received from the other end of serial communication does not match. Currently, if I lower the divisor value to "159", it works normally without errors. When operating at 3.3V, I understand that up to 32MHz is possible with an external oscillator input, but are there any other restrictions?

  • 0 in reply to MASAHIRO YANO
    Prodigy 10 points

    Excuse me for asking an additional question. In my previous question, I set the divisor value to "159", but after checking various things, I noticed that it behaved similarly to when running the "TL16CP754C" internal oscillator at 24MHz. The data sheet states that the external oscillator is limited to 32MHz, but will it hit an internal ceiling if it exceeds 24MHz?

  • 0 in reply to MASAHIRO YANO
    Guru 316690 points

    With a crystal, you can use at most 24 MHz. With an external oscillator, you can use up to 32 MHz.

    You are using an oscillator, so 24.576 MHz will work.

    To check the output baud rate, output bytes with the value 0x55 ("U" in ASCII) or 0xAA and measure the length of a bit with an oscilloscope; a divisor of 160 should result in 104.17 µs; for 159, 103.42 µs (9660 baud).

  • 0 in reply to MASAHIRO YANO
    TI__Guru 72771 points

    https://www.ti.com/lit/er/sllz058a/sllz058a.pdf?ts=1748624800643&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FTL16C754C

    The C versions of this device have a short bit bug (see document). Changing the divisor to make the bits a little longer is the work around to this issue.

    -Bobby