mirror of
https://github.com/sethm/symon.git
synced 2024-09-08 19:54:59 +00:00
795ccfde5d
Bug Fixes: - Fixed several bugs in the CPU that caused processor status flags to be set incorrectly. Instructions affected were: STA, STX, STY, CMP, CPX, CPY, BIT. - Made some internal-use-only methods on the CPU class private. - Fixed incorrect disassembly of (Indirect,X) and (Indirect),Y instructions. Although this didn't affect behavior, it certainly caused me some confusion in debugging. - Added missing "BCS" instruction to instruction table. Enhancements: - Now includes a full version of Lee Davison's Enhanced 6502 BASIC bundled as source code and a ROM image. Get that REAL COMPUTER EXPERIENCE!(tm) - If a file named "rom.bin" exists in the same directory where the simulator is executed, it will be loaded at addresses $d000-$ffff. - Gave the CPU an idle loop to make simulated timing a little more realistic (but this is still an area needing major improvement) - Changed the CPU's toString() method to give better debugging output. - Added a small typeahead buffer to the Console. - Better exception messaging. Misc: - Bumped version to 0.5, updated README.
37 lines
1005 B
NASM
37 lines
1005 B
NASM
;;
|
|
;; Read input from the keyboard, and echo to console.
|
|
;;
|
|
|
|
|
|
.alias iobase $c000
|
|
.alias iostatus [iobase + 1]
|
|
.alias iocmd [iobase + 2]
|
|
.alias ioctrl [iobase + 3]
|
|
|
|
.org $0300
|
|
|
|
start: cli
|
|
lda #$09
|
|
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
|