Add CRTC EhBASIC, switch char rom.

samples/ehbasic_crtc/min_mon.asm

@@ -0,0 +1,215 @@
+
+; minimal monitor for EhBASIC and 6502 simulator V1.05
+
+; To run EhBASIC on the simulator load and assemble [F7] this file, start the simulator
+; running [F6] then start the code with the RESET [CTRL][SHIFT]R. Just selecting RUN
+; will do nothing, you'll still have to do a reset to run the code.
+
+	.feature labels_without_colons
+	.include "basic.asm"
+
+; put the IRQ and MNI code in RAM so that it can be changed
+
+IRQ_vec	= VEC_SV+2		; IRQ code vector
+NMI_vec	= IRQ_vec+$0A	; NMI code vector
+
+; setup for the 6502 simulator environment
+
+IO_AREA		= $8800
+ACIAdata	= IO_AREA		; simulated ACIA r/w port
+ACIAstatus	= IO_AREA+1
+ACIAcommand	= IO_AREA+2
+ACIAcontrol	= IO_AREA+3
+
+	CRSR_L	= $20B
+
+
+; now the code. all this does is set up the vectors and interrupt code
+; and wait for the user to select [C]old or [W]arm start. nothing else
+; fits in less than 128 bytes
+
+.segment "MONITOR"
+	.org	$FC00			; pretend this is in a 1/8K ROM
+
+; reset vector points here
+
+RES_vec
+	CLD				; clear decimal mode
+	LDX	#$FF			; empty stack
+	TXS				; set the stack
+
+; Initialize the ACIA
+ACIA_init
+	LDA	#$00
+	STA	ACIAstatus		; Soft reset
+	LDA	#$0B
+	STA	ACIAcommand		; Parity disabled, IRQ disabled
+	LDA	#$1E
+	STA	ACIAcontrol		; Set output for 8-N-1 9600
+
+; set up vectors and interrupt code, copy them to page 2
+
+	LDY	#END_CODE-LAB_vec	; set index/count
+LAB_stlp
+	LDA	LAB_vec-1,Y		; get byte from interrupt code
+	STA	VEC_IN-1,Y		; save to RAM
+	DEY				; decrement index/count
+	BNE	LAB_stlp		; loop if more to do
+
+; now do the signon message, Y = $00 here
+
+LAB_signon
+	LDA	LAB_mess,Y		; get byte from sign on message
+	BEQ	LAB_nokey		; exit loop if done
+
+	JSR	V_OUTP		; output character
+	INY				; increment index
+	BNE	LAB_signon		; loop, branch always
+
+LAB_nokey
+	JSR	V_INPT		; call scan input device
+	BCC	LAB_nokey		; loop if no key
+
+	AND	#$DF			; mask xx0x xxxx, ensure upper case
+	CMP	#'W'			; compare with [W]arm start
+	BEQ	LAB_dowarm		; branch if [W]arm start
+
+	CMP	#'C'			; compare with [C]old start
+	BNE	RES_vec		; loop if not [C]old start
+
+	JMP	LAB_COLD		; do EhBASIC cold start
+
+LAB_dowarm
+	JMP	LAB_WARM		; do EhBASIC warm start
+
+
+ACIAout:	
+
+	PHA
+@loop:	LDA	ACIAstatus
+	AND	#$10
+	BEQ	@loop		; Wait for buffer to empty
+	PLA
+	STA	ACIAdata
+	RTS
+
+;;; Byte out to the CRTC
+;;;
+;;; 1. Increment cursor position.
+;;; 2. Scroll if necessary.
+;;; 3. Store new cursor position in CRTC.
+
+	CRSR_L	= $DE		; Cursor address (low)
+	CRSR_H	= $DF		; Cursor address (high)
+	COL_M	= 40		; Max Column
+	ROW_M	= 25		; Max Row
+	CRSR_C	= $E0		; Cursor Column #
+	CRSR_R	= $E1		; Cursor Row #
+
+CRTCout:
+	JSR	ACIAout		; Also echo to terminal for debugging.
+
+	;; 1. Is this an enter (cr/lf)?
+	;;   Set CRSR_C = 0.
+	;;   Increment CRSR_R.
+	;;   If CRSR_R > ROW_M, scroll..
+	CMP	#$0A
+	BEQ	@doenter
+	CMP	#$0D
+	BEQ	@doenter
+	
+	;; 1. Is this a backspace?
+	;;   IF CRSR_C == 0 && CRSR_R == 0
+	;;     Do nothing, already home
+	;;   If CRSR_C > 0
+	;;     Set CRSR_C = CRSR_C - 1
+	;;   Else
+	;;     Set CRSR_C = COL_M
+	;;     Set CRSR_R = CRSR_R - 1
+	;; 
+	CMP	#$08
+	BEQ	@dobs
+
+	;; Otherwise, this is a normal character
+	;; Do normal character stuff.
+	JMP	@done
+
+@doenter:
+@dobs:	
+@done:
+	RTS
+
+;
+; byte in from ACIA. This subroutine will also force
+; all lowercase letters to be uppercase.
+;
+ACIAin
+	LDA	ACIAstatus		; Read 6551 status
+	AND	#$08			;
+	BEQ	LAB_nobyw		; If rx buffer empty, no byte
+
+	LDA	ACIAdata		; Read byte from 6551
+	CMP	#'a'			; Is it < 'a'?
+	BCC	@done			; Yes, we're done
+	CMP	#'{'			; Is it >= '{'?
+	BCS	@done			; Yes, we're done
+	AND	#$5f			; Otherwise, mask to uppercase
+@done
+	SEC				; Flag byte received
+	RTS
+
+LAB_nobyw
+	CLC				; flag no byte received
+no_load				; empty load vector for EhBASIC
+no_save				; empty save vector for EhBASIC
+	RTS
+
+; vector tables
+
+LAB_vec
+	.word	ACIAin		; byte in from simulated ACIA
+	.word	CRTCout		; byte out to simulated ACIA
+	.word	no_load		; null load vector for EhBASIC
+	.word	no_save		; null save vector for EhBASIC
+
+; EhBASIC IRQ support
+
+IRQ_CODE
+	PHA				; save A
+	LDA	IrqBase		; get the IRQ flag byte
+	LSR				; shift the set b7 to b6, and on down ...
+	ORA	IrqBase		; OR the original back in
+	STA	IrqBase		; save the new IRQ flag byte
+	PLA				; restore A
+	RTI
+
+; EhBASIC NMI support
+
+NMI_CODE
+	PHA				; save A
+	LDA	NmiBase		; get the NMI flag byte
+	LSR				; shift the set b7 to b6, and on down ...
+	ORA	NmiBase		; OR the original back in
+	STA	NmiBase		; save the new NMI flag byte
+	PLA				; restore A
+	RTI
+
+END_CODE
+
+; sign on string
+
+LAB_mess
+	.byte	$0D,$0A,"Symon (c) 2008-2014, Seth Morabito"
+	.byte   $0D,$0A,"Enhanced 6502 BASIC 2.22 (c) Lee Davison"
+	.byte   $0D,$0A,"[C]old/[W]arm ?",$00
+
+
+; system vectors
+
+.segment "VECTORS"
+	.org	$FFFA
+
+	.word	NMI_vec		; NMI vector
+	.word	RES_vec		; RESET vector
+	.word	IRQ_vec		; IRQ vector
+