RS-232 UART

The RS-232 UART (Universally Asynchronous Receiver-Transmitter) is a serial protocol UART, allowing for a connection between a terminal and the DE2 Board. It is configured for 8-bit data, one stop bit, odd parity, and a baud rate of 115,200.

Device

RS-232 UART

Configuration

Two 32-bit mapped registers

Input/Output

Either

Address Base

0x10001010

Address Map

Address	R/W	Description
base	R/W	Data Register 23:16 - Number of characters available to read (after this read - see Notes) 15 - read data valid 9 - parity error 7:0 - the data itself
base+4	R/W	Control Register 23:16 - Spaces available for writing 9 - Write interrupt is pending 8 - Read interrupt is pending 1 - Enable write interrupts 0 - Enable read interrupts

Initialization

None

Interrupts

Triggered	On data-received or able to send (see below)
IRQ Line	10
Enable	Set bit 1 and/or 0 in the Control Register for write and read interrupts respectively.
Acknowledge	Read (write) interrupts acknowledged by reading (writing) to the Data Register

Hardware Setup

Plug the serial cable into the serial outlet on the DE2 Board (also see Notes)

Reference

Full documentation from Altera.
Section 2.5 of the DE2 Media Computer Manual

Notes

To communicate through the RS-232, you must set up a terminal to send and receive characters. Open the Conport program (in the lab, this can be found on the network drive, X:\TTERMPRO, as ttermpro.exe), ensure that the Baud Rate is set to 115200 (for the default system, or whatever your baud rate is in a custom system), and ensure that it is communicating through CON1.

Assembly Example: Receiving a character through the RS-232 UART

POLL:
    movia r7, 0x10001010 /* r7 now contains the base address */
    ldhio r2, 2(r7) /* Load from the UART */
    beq   r2, r0, POLL /* If this is 0 (branch true), data is not valid */
    ldwio r2, 0(r7)

C Example: Sending "Hello World" through the UART

#define RS232_UART_DATA ((volatile int*) 0x10001010)
#define RS232_UART_CONTROL ((volatile int*) (0x10001010+4))

int main()
{
    unsigned char hwld[] = {'H','e','l','l','o',' ','W','o','r','l','d','\0'};
    unsigned char *pOutput;

    pOutput = hwld;
    while(*pOutput) //strings in C are zero terminated
    {
         //if room in output buffer
         if((*RS232_UART_CONTROL)&0xffff0000  ) 
         {
            //then write the next character
            *RS232_UART_DATA = (*pOutput++); 
         }
     }
}