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I'm using dosbox to allow 16 bit programs to run and TASM. my OS is windows 8 and I don't seemm to have any trouble with running any other interrupts except the 14h interrupt specifically transmit and receive. I use two USB to UART modules with their RX and TX tied to one another (rx->tx, tx->rx) and their grounds are connected as well. My problem is that it just won't transmit. The modules are fine as I tested them both with realterm.

here's my code for transmit.

.model small  
.stack   
.data  
.code  
main proc far  
mov ax,@data  
mov ds,ax  
mov al,11100011b ;baud rate set to 9600  
mov dx,0 ;com port 1, yes i've configured the comport on both pc and conf file of dosbox  
int 14h  
mov ah,01  
mov al,42h ;character to transmit, letter B  
mov dx,0h  
int 14h  
mov ah,4ch  
int 21h  
main endp  
end main
Devolus
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John Chua
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  • What have you done yet.? – Aishvarya Jaiswal Dec 13 '13 at 05:15
  • I've just connected two PCs using two USB to UART modules and ran a transmit code from one PC and a receive code in the other, unfortunately nothing happens. I tried using real term on both PCs and they transmit and receive just fine. – John Chua Dec 13 '13 at 05:32
  • You don't mention what you've done with the flow control lines. Windows might be enforcing flow control on you that you don't want. Make sure to disable it with the appropriate `mode COMx:` commands outside your DOSBOX. – Joe Z Dec 13 '13 at 13:41

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