[参考译文] TRF7970A：原始写入的工作原理

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https://e2e.ti.com/support/wireless-connectivity/other-wireless-group/other-wireless/f/other-wireless-technologies-forum/1114925/trf7970a-how-raw-write-works

器件型号：TRF7970A

您好！

我正在编写 sloc297c 示例代码。我主要了解 trf7970a 的工作原理。我无法理解是对 IC 进行 SPI 原始写入。

uint8_t ISO14443A_sendPollCmd(uint8_t cmd)
{
    uint8_t offset = 0;
    uint8_t status = STATUS_FAIL;

    g_pui8TrfBuffer[offset++] = 0x8F; // Reset FIFO
    g_pui8TrfBuffer[offset++] = 0x90; // Send without CRC
    g_pui8TrfBuffer[offset++] = 0x3D; // Write Continuous
    g_pui8TrfBuffer[offset++] = 0x00; // Length of packet in bytes - upper and middle nibbles of transmit byte length
    g_pui8TrfBuffer[offset++] = 0x0F; // Length of packet in bytes - lower and broken nibbles of transmit byte length
    g_pui8TrfBuffer[offset++] = cmd;  // Send the polling command from function input - either REQA (0x26) or WUPA (0x52)

    // Issue the ISO14443A Polling Command
    TRF79xxA_writeRaw(g_pui8TrfBuffer, offset);

    g_sTrfStatus = TRF79xxA_waitRxData(3, 10); // 3 millisecond TX timeout, 10 millisecond RX timeout

    if (g_sTrfStatus == RX_COMPLETE) // Tag detected - could be either a single or collided tag
    {
        status = STATUS_SUCCESS;
    }
    else if (g_sTrfStatus == COLLISION_ERROR)
    {
        status = STATUS_SUCCESS; // "A PCD detecting a collision in any bit of (b16 to b1) shall commence with the first step of the anticollision loop."
    }

    return status;
}

上面的函数向 PICC 发送 REQ 命令。但在 Req cmd 之前、有5 个额外的字节。写入该数据时未指定寄存器地址。如何处理该数据。例如、第一个数据是0x8F、它会重置 FIFO、看起来它是一个命令、但我们不为此过程指定寄存器。您能否解释或提供任何资源来帮助我理解它？

此致。

3 年多前