Humm.. Then the debug monitor comes from the EEPROM on the board.
Set 'SW2: EEPROM Enable' on the CY3681 to 'No EEPROM' temporarily.


Our CY3681 is busy now, so I checked it on our own test board.

Download this HEX directly to the FX2 using CyConsole (or EZ-USB Control Pannel), without any debug monitor.
This HEX is generated by the source code as follows.
You should see signal on RXD0OUT, when it is not disturbed by the debug monitor.

:1000030090E600E054E74410F090E6727408F0754F
:0C00130098133099FDC29975995580F63C
:0300000002001FDC
:0C001F00787FE4F6D8FD7581070200032D
:00000001FF

// test_uart0.c
//  test for UART0 mode 0
//
// command line to build this file
//      c51 test_uart0.c db oe code small moddp2
//      bl51 test_uart0.obj TO test_uart0 RAMSIZE(256) XDATA(1900h)
//      oh51 test_uart0 HEXFILE(test_uart0.hex)

#define ALLOCATE_EXTERN
#include "fx2.h"
#include "fx2regs.h"

void main(void)
{
    // set the CPU clock to 48MHz
    CPUCS = ((CPUCS & ~bmCLKSPD) | bmCLKSPD1) ;

    PORTECFG  =  0x08;  // enable RXD0OUT
    SCON0     =  0x13;  // mode 0, receive enabled, baud CLKOUT/12, TI = 1, RI = 1

    while(1){
        if ( TI ){
            TI = 0;
            SBUF0 = 0x55;
        }
    }
}

Tsuneo