Serial Communication Interface (SCI) - The HCS12/9S12: An Introduction to Software and Hardware Interfacing - page 468

The C language version of the function is as follows:
char getcSCI0 (void)
{

while(!(SCI0SR1 & RDRF));

return (SCI0DRL);

}

▲

Example 9.6
▼

Write a subroutine that outputs a NULL-terminated string pointed to by index register X
to the SCI0 using the polling method.
Solution: The subroutine will call putcSCI0() repeatedly until all characters of the string have
been outputted.
putsSCI0 ldaa 1,x 1 ; get a character and move the pointer

beq done ; is this the end of the string?

jsr putcSCI0

bra putsSCI0

done rts
The C language version of the program is as follows:
void

putsSCI0 (char *cx)

{

while (!(*cx)) {

putcSCI0(*cx);

cx 11 ;

}

}

▲

Example 9.7
▼

Write a subroutine that inputs a string from the SCI0 module. The string is terminated by
the carriage return character and must be stored in a buffer pointed to by index register X. This
subroutine must allow the user to backspace to erase errors.
Solution: The subroutine will call getsSCI0() repeatedly until the carriage return character is
inputted.
getsSCI0 jsr getch

cmpa #CR ; is it a carriage return?

beq qi

staa 0,x ; save the character and increment the pointer

jsr putch ; echo it back to SCI0

cmpa #BS ; is it a backspace character?