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Why not clear buffer

Guojun Li

Please help me to find the problem:

In my program, I use UART to receive data by UART interrupt, please see following.

#define uchar unsigned char
#define DATALTH 255

volatile uchar SerBuffer;
volatile uchar I_ptr;

void isr_UART(void) interrupt SIO_VECTOR using 0
{
uchar c;

if(RI)
{
c = SBUF;
RI = FALSE;
SerBuffer[I_ptr & (DATALTH -1)] = c;
}
}

But when I use
memset(SerBuffer,0x00,DATALTH);
or
Addr = strchr(SerBuffer,0x22);
to clear "SerBuffer" or search
0x22 from "SerBuffer" and during the progress there are data received by UART, then there will be serious error.

Please tell me the reason.
thank you.

  • 0

    Use the &ltpre&gt and &lt/pre&gt tags when posting code.

    You seem to have mis-typed the code when you posted it:

    volatile uchar SerBuffer;

:

SerBuffer[I_ptr & (DATALTH -1)] = c;

:

memset(SerBuffer,0x00,DATALTH);
    You have defined 'SerBuffer' as a uchar, but you are using it as an array/pointer.

  • 0 in reply to Andrew Neil

    I'm sorry for mis-type.
    In fact, I define "SerBuffer" with

    volatile uchar SerBuffer[DATALTH];

    Thanks.

  • 0

    I don't know exactly if it's going to solve your problem or not but, when I was glancing your code something caught my attention...

    void isr_UART(void) interrupt SIO_VECTOR using 0

    You declared your ISR using register bank 0, where you already in the bank 0 during the normal program execution ?

    If yes, it could be your problem...

  • 0 in reply to Alex Ruiz

    If as you thought, why Keil not push all the variables which are used in normal progress into stack when interrupt occur.

    I'l test as you said.

    Thanks

  • 0 in reply to Guojun Li

    why Keil not push all the variables which are used in normal progress into stack when interrupt occur.?

    Keil didn't push and pop all the variables because you desired when you added the using X keyword.

    The compiler switch the register bank ( PSW , so it doesn't need to push and pop the registers during the ISR, with this operation you save some bytes ( that is vital in some applications ) and execution speed.

    You can "let" the compiler use PUSHs and POPs, you need to use a directive and delete the using X keyword from your function, prototypes and so on.