Type latin alphabet from "A" to "Z" on display screen.
The initial symbol "A" has code 65=41h. So we put it into R0 and call ROM subroutine, that outputs character. The next letter can be get after increment of R0. If the result exceeds 5Ah ("Z"), the cycle ends.
| Address | Code | Operation | Comments |
|---|---|---|---|
0000 | 0E6D |
30 ==> SP | set SP for correct |
0004 | 01D0 |
41 ==> R0 | first symbol code |
0008 | 9C0D |
call subroutine | output to screen |
000C | 2210 |
R0 + 1 ==> R0 | next symbol |
000E | 04D0 |
compare R0 with 5A | code <= "Z"? |
0012 | 6DF4 |
if <=0, then pc=pc+F4 | repeat cycle (to 0008) |
0014 | 0F00 |
halt | stop |
Try and examine, how it works in "E97".