Re: [Simulavr-devel] UART

[Keith Gudger]

On Thu, 20 Nov 2003, Theodore A. Roth wrote:

> > I have some questions about simulavr behavior with my uart code that I'm
> > hoping your experience can help me find the answers.
> >
> > First, it appears that when starting up, simulavr executes the "read"
> > routine passed to vdev_construct.  I haven't noticed this before, but
> > maybe it's just the way my code works this time.  Is this possible?  (It's
> > showing up a message from that function even before I get the "Waiting on
> > port 1212 ... message.)
> 
> I need more info. Can you send me the output message in question?
> 
Here's what happens at startup:
./simulavr -g -d atmega128

Simulating a atmega128 device.

MESSAGE: file decoder.c: line 3517: generating opcode lookup_table

Enter 9 bits of hex data to read into the uart at address 0x002c:

The new information I have, is that since the mega128's 2nd UART is not in
the I/O space, this does not happen for the 2nd UART.  Here is the code
that generates this input request:

    if ( offset == UART_UDR_ADDR )
    {
        uart_t->usr &= ~mask_RXC ; /* clear RXC bit in USR */
        return uart->udr_rx = uart_port_rd( addr );

This code is in my uart_read routine.  This means that this code gets
called *before* I even connect!  Any idea why this happens?  As I
mentioned, it only happens for the UART configured in I/O space.

> >
> > Second, the interrupt call-back gets installed as an
> > avr_core_async_cb_add, the same as all the other files I've worked on.
> > However, I notice that the call-back routine gets called *a lot*.  Even
> > when it looks like nothings happening.  Is this normal?  Should I be
> > worried?
> 
> The callbacks should get called a lot. Clock callbacks get called for
> _every_ clock cycle, async callbacks for every instruction.
> 

Here is what happens next, when I *do* connect:

Waiting on port 1212 for gdb client to connect...
Connection opened by host 127.0.0.1, port 45716.
MESSAGE: file avrcore.c: line 826: Raising irq # 29 [IRQ_USART0_UDRE at
0x4c]
MESSAGE: file avrcore.c: line 1035: Vectoring to irq at addr:76 offset:0
MESSAGE: file avrcore.c: line 826: Raising irq # 29 [IRQ_USART0_UDRE at
0x4c]
MESSAGE: file avrcore.c: line 826: Raising irq # 29 [IRQ_USART0_UDRE at
0x4c]
MESSAGE: file avrcore.c: line 826: Raising irq # 29 [IRQ_USART0_UDRE at
0x4c]
MESSAGE: file avrcore.c: line 826: Raising irq # 29 [IRQ_USART0_UDRE at
0x4c]
MESSAGE: file avrcore.c: line 826: Raising irq # 29 [IRQ_USART0_UDRE at
0x4c]
MESSAGE: file avrcore.c: line 826: Raising irq # 29 [IRQ_USART0_UDRE at
0x4c]
MESSAGE: file avrcore.c: line 826: Raising irq # 29 [IRQ_USART0_UDRE at
0x4c]
MESSAGE: file avrcore.c: line 826: Raising irq # 29 [IRQ_USART0_UDRE at
0x4c]
MESSAGE: file avrcore.c: line 826: Raising irq # 29 [IRQ_USART0_UDRE at
0x4c]
MESSAGE: file avrcore.c: line 826: Raising irq # 29 [IRQ_USART0_UDRE at
0x4c]
MESSAGE: file avrcore.c: line 826: Raising irq # 29 [IRQ_USART0_UDRE at
0x4c]
MESSAGE: file avrcore.c: line 826: Raising irq # 29 [IRQ_USART0_UDRE at
0x4c]
MESSAGE: file avrcore.c: line 826: Raising irq # 29 [IRQ_USART0_UDRE at
0x4c]


Do you think that this is something weird I've put in my code, or should I
expect this?

Thanks.
Keith