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Keil Memory window not updating

Akshay Immanuel

Im using LPC1778 to simulate SSP1. The usermanual states that DR for SSP1 is at address 0x40030008. When I transmit data, I immediately receive data into the receive buffer(RNE flag in status register gets set) and also the value loaded into DR shown by Keil is not the value loaded by me into the DR.

//Send data
U8 spi_send(U8 bChannelNo,U8 *pBufferPtr,U8 bLength)
{
        U8 bDummy=0;
        U8 bReturn_val=0;
        bDummy++;
        bDummy=0;

        switch(bChannelNo)
        {
                case 0:
                        ssp_12=LPC_SSP0;
                break;

                case 1:
                        ssp_12=LPC_SSP1;
                break;

                case 2:
                        ssp_12=LPC_SSP2;
                break;

                default:
                        ssp_12=LPC_SSP0;
                break;
        }

        set_timeout2(10000);
        do
        {
                if(!(ssp_12->SR & (1<<4))) /*not busy*/
                {
                        if(ssp_12->SR & (1<<1)) /*tnf*/
                        {
                                ssp_12->DR=*pBufferPtr;
                                pBufferPtr++;
                                bLength--;
                        }
                }
        }while(((LPC_TIM2->TC) < (LPC_TIM2->MR1)) && ((LPC_TIM2->TC) != (LPC_TIM2->MR1)) && (bLength != 0));

        if(bLength==0)
        {
                bReturn_val=1;
        }
        return bReturn_val;

}

//receive

U8 spi_receive(U8 bChannelNo,U8 bLength,U8 *pRxDataBuff)
{
        U8 bReturn_val=0;
        U8 bLoc=0;
        switch(bChannelNo)
        {
                case 0:
                        ssp_12=LPC_SSP0;
                break;

                case 1:
                        ssp_12=LPC_SSP1;
                break;

                case 2:
                        ssp_12=LPC_SSP2;
                break;

                default:
                        ssp_12=LPC_SSP0;
                break;
        }

        set_timeout2(10000);
        do
        {

                if(!(ssp_12->SR & (1<<4))) /*not busy*/
                {
                        if(ssp_12->SR & (1<<2)) /*rne*/
                        {
                                pRxDataBuff[bLoc]=ssp_12->DR;
                                bLength--;
                                bLoc++;
                        }
                }
        }while(((LPC_TIM2->TC) < (LPC_TIM2->MR1)) && ((LPC_TIM2->TC) != (LPC_TIM2->MR1)) && (bLength != 0));

        if(bLength==0)
        {
                bReturn_val=1;
        }
        return bReturn_val;
}

I used CMSIS driver examples for lpc1778 but still data is immediately received on sending and memory address doesnt contain the tx data. Why is Keil doing that?

Parents
  • 0 in reply to Akshay Immanuel

    The idle state for SPI communication is 0xff (or whatever word length the device is configured to send).

    So it's quite common to define protocols where 0xff represents "null" data that can be thrown away.

    But since SPI is always two-way, i.e. full duplex, and the slave can only send when the master sends - since the master owns the clock line and creates the bit timing - the way to implement semi-duplex communication is:
    - the server sends out the words of the query, while consuming and throwing away the same number of words received.
    - the server then sends out the same number of dummy words as the client response is long, while picking up the received words and storing in the receive buffer.

    So the server needs to know how long the slave response will be. Or the server needs to be able to decode the response words one at a time to detect how long the answer is.

    Please don't duplicate text like that in your answers. Use "" to show what part of the text that is quoted - quotation marks are labeled like that for a reason. It's quite confusing to have questions/answers randomly mixed.

Reply
  • 0 in reply to Akshay Immanuel

    The idle state for SPI communication is 0xff (or whatever word length the device is configured to send).

    So it's quite common to define protocols where 0xff represents "null" data that can be thrown away.

    But since SPI is always two-way, i.e. full duplex, and the slave can only send when the master sends - since the master owns the clock line and creates the bit timing - the way to implement semi-duplex communication is:
    - the server sends out the words of the query, while consuming and throwing away the same number of words received.
    - the server then sends out the same number of dummy words as the client response is long, while picking up the received words and storing in the receive buffer.

    So the server needs to know how long the slave response will be. Or the server needs to be able to decode the response words one at a time to detect how long the answer is.

    Please don't duplicate text like that in your answers. Use "" to show what part of the text that is quoted - quotation marks are labeled like that for a reason. It's quite confusing to have questions/answers randomly mixed.

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