mirror of https://github.com/sethm/symon.git
37 lines
1005 B
NASM
37 lines
1005 B
NASM
;;
|
|
;; Read input from the keyboard, and echo to console.
|
|
;;
|
|
|
|
|
|
.alias iobase $8800
|
|
.alias iostatus [iobase + 1]
|
|
.alias iocmd [iobase + 2]
|
|
.alias ioctrl [iobase + 3]
|
|
|
|
.org $0300
|
|
|
|
start: cli
|
|
lda #$0b
|
|
sta iocmd ; Set command status
|
|
lda #$1a
|
|
sta ioctrl ; 0 stop bits, 8 bit word, 2400 baud
|
|
|
|
;; Load a character from the keyboard and store it into
|
|
;; the accumulator
|
|
|
|
getkey: lda iostatus ; Read the ACIA status
|
|
and #$08 ; Is the rx register empty?
|
|
beq getkey ; Yes, wait for it to fill
|
|
lda iobase ; Otherwise, read into accumulator
|
|
|
|
;; Write the current char in the accumulator to the console
|
|
|
|
write: pha ; Save accumulator
|
|
writel: lda iostatus ; Read the ACIA status
|
|
and #$10 ; Is the tx register empty?
|
|
beq writel ; No, wait for it to empty
|
|
pla ; Otherwise, load saved accumulator
|
|
sta iobase ; and write to output.
|
|
|
|
jmp getkey ; Repeat
|