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TSS521 mbus

Other Parts Discussed in Thread: MSP430G2553, TSS521

Dear, 

I am making a new design about mbus . I am using MSP430G2553 as MCU and TSS521 or TSS721 as transceiver. I have some questions?

1- Which pins I should use, RX-TX or RXI-TXI? what is the differences about code side?

2-I use battery for mcu and transceiver? How ı connect the transciever power pins? İs there a sample circuit?

Thanks in advance..

  • Hi Umut,

    1. Based on Figures 6 & 7 of the TSS521 datasheet I would connect UCA0RXD to TXI and UCA0TXD to RXI. The difference, as Figures 1 & 2 show, have to deal with the inactive state of the line so if using normal USCI operation you want the lines inactive low, hence TXI and RXI.

    2. The example application circuits from the TSS521 datasheet should be able to answer this question: www.ti.com/.../tss521.pdf

    Regards,
    Ryan
  • Hi Ryan,

    first thanks for everything.

    I have some questions to make it clear. I found some things about TSS721 (like TSS521).

    1- The below information is correct?Is the TXI should be high (VCC) while not transferis active?

    2-I put below a design of TSS721. In design there is no connection with pin BAT and VDD? But this works. In datasheet there is no design sample like it. Could you explain it me, please?

  • Umut,

    1) Based on my interpretation of Figures 2 and 3 of the datasheet, TXI and RXI are low (GND) when the transfer is not active. This case is inversed for the TX and RX pins (high state, Vcc, during inactivity).

    2) As Figures 7 and 8 of the datasheet show the VDD and BAT pins are most commonly directly connected to either a standalone supporting capacitor CSTC > 50 µF or a battery with parallel system stabilizing capacitor.

    Regards,
    Ryan
  • Hi Ryan,

    I designed circuit again but it does not work:(( and I have to finish this project in one week.

    I designed figure 8 with below value:

    Rload:100k
    Cvdd:100nF
    Rris:100 ohm
    Csc:10nF
    Rridd:29,2K
    Cstc:10uF / 50V
    Cssc:100 nF

    The mcu does not receive any commend frpm mbus line. but it sends different datas.
    what is my mistake with values?

    if some values are wrong , what they must be?

    Regards,
    usueslue

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