"mcs-51 switch" example dosen't work.

arcachofo wrote:It is working for me.
Note that 8051 Reset is active High, so to get it working it must be Low.

arcachofo wrote:I see, you are using development branch.
I will have a look.

And all registers exerpt PC is empty in the MCU monitor.

If I remember well, the output pins of C51 MCU family are open collector.

And all registers exerpt PC is empty in the MCU monitor.

Why PC+3 is pushed to the stack?

LCALL calls a subroutine located at the indicated address. The instruction adds
three to the program counter to generate the address of the next instruction and
then pushes the 16-bit result onto the stack (low byte first)

Code:

virtual void INTERRUPT( uint32_t vector ) { CALL_ADDR( vector ); }

Code:

void McuCpu::CALL_ADDR( uint32_t addr ) // Used by MCU Interrupts:: All MCUs should use or override this
{
    PUSH_STACK( m_PC );
    setPC( addr );
    m_mcu->cyclesDone = m_retCycles;
}

arcachofo wrote:

Why PC+3 is pushed to the stack?

Instruction LCALL does that:

LCALL calls a subroutine located at the indicated address. The instruction adds
three to the program counter to generate the address of the next instruction and
then pushes the 16-bit result onto the stack (low byte first)

royqh1979 wrote:But before LCALL() (which is called by Exec()) called, m_PC has already been updated  ( m_tmpPC has been increased by 3 while decoding) and pointing to the instruction next to LCALL.

But before LCALL() (which is called by Exec()) called, m_PC has already been updated ( m_tmpPC has been increased by 3 while decoding) and pointing to the instruction next to LCALL.

And the decode of mov reg, Rx seems not right. It should mov the content of Rx, not address of Rx.

Code:

void I51Core::operRgx() { m_op0 = m_RxAddr; }//{ m_op0 = m_dataMem[m_RxAddr]; }
// Change to:
void I51Core::operRgx() { m_op0 = m_dataMem[m_RxAddr]; } //{ m_op0 = m_RxAddr; }

arcachofo wrote:

And the decode of mov reg, Rx seems not right. It should mov the content of Rx, not address of Rx.

I see...
Maybe you can try the commented part:

Code:

void I51Core::operRgx() { m_op0 = m_RxAddr; }//{ m_op0 = m_dataMem[m_RxAddr]; }
// Change to:
void I51Core::operRgx() { m_op0 = m_dataMem[m_RxAddr]; } //{ m_op0 = m_RxAddr; }

Maybe I changed it for some reason and forgot to return to the original.

operRgx() is also used in other places. So maybe it should be kept and create a new method for instructions 0x8x only.