;SINGLE REGISTER READ
;	Requirements: PCB v0.94c, ATMEGA32 FW v0.94c
;	VIA Base Address = $2000 (8192 DECIMAL)
;	- write desidered register in $0280,
;	- execute program
;	- read value in $0281
;	RESET after run may be necessary only in WOZ Monitor. From BASIC: CALL 1536.

define DDRB $2002
define DDRA $2003
define IRB $2000
define IRA $2001
define REGISTER $0280
define VALUE $0281

LDA #$0		;all PORTB channels set as input
STA DDRB	;set DDRB
LDA #$40	;all PORTA channels except bit6 (PA6, RW signal) are input
STA DDRA	;set DDRA
LOOP:
	LDA #$80	;load 10000000 in A (pattern of STROBE signal coming from ATMEGA)
	LDX IRB		;load IRB in X
	BIT IRA		;check for STROBE signal=HIGH in IRA memory location
	BEQ LOOP	;if not, loop again
	LDA IRA		;load current register index to A
	CMP REGISTER	;compare to requested register index
	BNE LOOP	;if not loop again
	STX VALUE	;store X into VALUE
	RTS

0600: a9 00 8d 02 20 a9 40 8d 03 20 a9 80 ae 00 20 2c 
0610: 01 20 f0 f6 ad 01 20 cd 80 02 d0 ee 8e 81 02 60