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Serial interrupts on Mx2 chip

Sundeep Subbarau

Hi
This question is about serial interrupts on the 8051 based extended memory chip (P87C51Mx2).

The transmit interrupt TI_0 is supposed to be set when a character is written to S0BUF. This is not happening.
My initialization settings are as follows (I'm initializing both the UART channels)

T2CON = 0x30;
RCAP2H = 0xFF; // BAUD for UART0 - 9600
RCAP2L = 0xB8;

S0CON = 0x50;
S1CON = 0x50;

TXD   = 1;
RXD   = 1;
TXD1  = 1;
RXD1  = 1;
ES0   = 1;
ES1   = 1;

S0STAT = 0x00;
S1STAT = 0x00;

TR2 = 1;

BRGCON = 0x00; //UART1 baud - 38400
BRGR1 = 0x01;
BRGR0 = 0x10;
BRGCON = 0x01;


I'm setting the bits TI_0 or TI_1 when I've data to transmit and resetting it in the ISR. But what I observe is that the ISR is entered only once and never again!

The processor runs at 6 clock mode and 11.0592 MHz oscillator frequency.

Any help would be appreciated.

warm regards,
Sundeep M S

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  • 0 in reply to Sundeep Subbarau

    The S0BUF is loaded in the ISR and I expect that TI_0 is set so that the next character in my array is loaded to S0BUF and so on.
    your expectation is correct, TI_0 should be set on completion of the transmission.

    Based on the above, your problem is not S0BUF/TI, but something else.
    Possibilities:
    1)the interrupt get disabled (check IE)
    2)the progrem gets hung elsewhere
    3)the simulator - It is a simulator not the real thing - does not simulate TI_0 correctly due to setup or malfunction.
    4) I tend to recall that in the MX you can redirect TI interrupts to an unique vector, leaving the standard vector for RI only. try making an ISR for that vector and see if that is wwhere you go.

    Erik

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  • 0 in reply to Sundeep Subbarau

    The S0BUF is loaded in the ISR and I expect that TI_0 is set so that the next character in my array is loaded to S0BUF and so on.
    your expectation is correct, TI_0 should be set on completion of the transmission.

    Based on the above, your problem is not S0BUF/TI, but something else.
    Possibilities:
    1)the interrupt get disabled (check IE)
    2)the progrem gets hung elsewhere
    3)the simulator - It is a simulator not the real thing - does not simulate TI_0 correctly due to setup or malfunction.
    4) I tend to recall that in the MX you can redirect TI interrupts to an unique vector, leaving the standard vector for RI only. try making an ISR for that vector and see if that is wwhere you go.

    Erik

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