P1012 SPI queries

[ankitmaurya]

Hi I am using P1012 ESPI in master mode and have few queries regarding it . Can someone please answer these ?

1.The  eSPI Event Register (SPIE) reports events . I do not wan't interrupts , so I have set SPIM to 0 to mask the interrupts. The manual says that we should clear SPIE by writing a 1. Now suppose I have set 

eSPI Mode Register (SPMODE) to  0x80001D03 which enables interrupts , and sets RXTHR -3 , TXTHR -29. I wan't to do a 4 byte write and a 4 byte read , hence the values of RXTHR and TXTHR.  For writing I use the following code -

 *******************************************************

For writing

********************************************************* 

 spieData = SPI_REG_READ_32 (SPIE);

 /*check if TNF is 1 i.e TX fifo is not full , and TXT is set i.e Transmit FIFO has at most

  * TXTHR -1 (29-1) - 28 bytes. So we can do a 4 byte write.

  */

  while( (spieData & (0x100) == 0) || (spieData & (0x800))  == 0 ){

    /*SPI core not ready , wait */

    if(timeout >= sendSpansionFlashTransTimeout){

    printf("%s :Error !! TNF/TXT not set spieData = 0x%08x\n",__FUNCTION__,spieData);

    return ERROR;

    }

    timeout = timeout+1;

    sysUsDelay (100);

  }

/*can write the data now */

SPI_REG_WRITE_32 (SPITF, *(VUINT32 *) cmd);

*****************************************************

For reading

*****************************************************

spieData = SPI_REG_READ_32 (SPIE);

timeout =0;

/*check if RNE(22nd bit) is 1 i.e RX fifo is not empty , and RXT(18th bit) is set i.e Receive FIFO has at least

* RXTHR +1 (3+1) = 4 bytes. So we can do a 4 byte read.

*/

while( (spieData & (0x200) == 0) || (spieData & (0x2000))  == 0 ){

    /*SPI core not ready , wait */

    if(timeout >= readIdReceiveTimeout){

    printf("%s Error !! RNE/RXT not set spieData = 0x%08x in empty buffer\n",__FUNCTION__,spieData);

    return ERROR;

    }

    timeout = timeout+1;

    sysUsDelay (100);

}

/* read the SPIRF  in 32 bit, to empty the buffer */

readData = SPI_REG_READ_32 (SPIRF); 

Is this implementation correct ? Is there a better way to read /write ?

2. Suppose (SPMODE) is  0x80001D0 and SPIM to 0x0.  I have more than 4 bytes in my RX FIFO so I assume that the RXT (bit 18) of SPIE will be set. Now I read few bytes and the number of bytes become less than 4 bytes , say 2 bytes  then will the RXT(bit 18) clear automatically or I have to clear it every time it is set to 1 , so see any further changes. Is this behaviour same for every bit of SPIE i.e I have to clear every time it sets to 1 ?(As mentioned RNE,TNF,RXCNT and TXCNT are not affected by clear SPIE).

3. Suppose I have to read 65000 bytes from a flash with 24 bit address and one byte instruction.. So I set the SPCOM to 0x0004FDEB . Now the rx buffer is only 32 bytes but here the CPU will send 65000+4 = 65004 clock cycles so the CPU rx buffer will overflow . Am I correct ? If yes then what is the recommended way to read large amount of data from a flash , say 16mb, which will involve multiple SPCOM writes.

4. What happens when the EN (bit 0) of the SPMODE is toggled from 0 to 1  OR 1 to 0. Which all registers are impacted ? What happens if the frame is not transmitted fully ?

Thanks in advance.

[ankitmaurya]

Thanks for the reply . Sorry If some of my questions were not clear.

1.Yes , you are correct I should read SPIE in the while loop. I missed it.

2.The SPMODE is set to 0x80001D03(it was a typo) and SPIM to 0x0. My question is regarding the SPIE register.    

   Suppose the TXE bit is set in the ESPI. I read that bit and did a write , now I wan't to read again the TXE bit to 

   determine when the TX FIFO becomes empty. Can I read the TXE bit again , without clearing it the first time or do I have to clear it every time I read it, so that I can get proper status next time I read the TXE bit. Does similar logic clear /read logic applies to DON,RXT , RXF and TXT bit as well ?

3. Will read less then 32 bytes to avoid overflow.

4. Suppose I have written 0x00000004 to SPCOM(so number of characters in the frame is 5). Now , suppose after sending 2 characters I stopped(due to some error). Now I wan't to start the complete transaction again. So again

I write 0x00000004 to SPCOM and this time I sent 5 characters , but in this case I do not see the DON bit in SPIE being set to 1 . Even if I do soft reset of CPU and try the transaction again I still see DON bit in the SPIE is not set to 1.  Why is this ? How to handle such broken writes/reads ?

5. Is there a way to reset the CPU espi block ?

Thanks,
Ankit

[r8070z]

Have a great day,

1. I do not see where you read status to the spieData in the while loops. So you will check the same value in the loop until timeout in case when the SPI was not ready before the while{}.
2. You wrote “(SPMODE) is  0x80001D0”. According to the ESPI_SPMODE description in the manual you do not enable eSPI, set reserved bits and set 5-bit RXTHR field to 0x10, i.e. 32 bytes threshold.
   The RXCNT and TXCNT are read only fileds. While the RXT ( RNE, TNF) bit has been set it can be cleared by writing 1 only.
3.   You should estimate you the system load, the CPU response delay, eSPI bit rate and then make conclusion. The safe way is using transactions with length less than FIFO depth.
4.   >What happens when the EN (bit 0) of the SPMODE is toggled from 0 to 1  OR 1 to 0.
    SPI controller is enabled or disabled

> Which all registers are impacted ?

This question is fuzzy. You should care for SPMODE itself. Any bits in SPMODE must not change when EN is set.

>What happens if the frame is not transmitted fully ?

The frame will not be transmitted fully.

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