Datasheet

5–8

; receive to get back to monitor

; with ESC

MOV #00h,&03DEh ; prepare software UART only for

; use in the ROM-Monitor

(&05DEh on the MSP430X33

ENDL JMP ENDL

UART BR &INT_RXTX

.sect “Int_Vect”,03E0h ; 05E0h on the MSP430X33x

.word RESET ; Reset

.word UART ; UART Routine

.word RESET ; Reset

.end

5.6 Receiving a Character

A character received using the RS232 interface is written from the INT_RXTX interrupt routine into memory

location 210h. After performing a reset, this memory location contains zeros. Each byte (not equal to zero)

received is stored in memory location 210h.

The content of memory location 210h is checked to determine whether or not a byte has been received. After

reading the byte, this location must be cleared. The next-received character will overwrite memory location

210h with a new byte.

The following code is an example of receiving a character and transmitting the same character back.

WDTCTL .equ 0120h

WDTHold .equ 80h

WDT_wrkey .equ 05a00h

TXCHAR .equ 0FFD2h

TXTABLE .equ 0FFD4h

PREPRX .equ 0FFD6h

PREPTX .equ 0FFD8h

INT_RXTX .equ 0FFDAh

TXDATA .equ 020Eh

RXBUF .equ 0210h

.text 0240h

RESET MOV #03DEh,SP ; #05DEh on the MSP430X33x

MOV #(WDTHold+WDT_wrkey),&WDTCTL ; stop Watchdog Timer

EINT ; enable interrupt

RX MOV #0AA55h,&03DEh ; select user interrupt vector

; table (&05DEh on MSP430X33x)

CALL &PREPRX ; prepare software UART for