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Preparing for real implementation

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This commit is contained in:
Seth Morabito 2014-08-15 12:48:54 -07:00
parent 70ab2a6fc2
commit ed1d5f999b
2 changed files with 50 additions and 85 deletions
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2
samples/ehbasic_crtc/basic.asm
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@ -437,7 +437,7 @@ Ibuffs = IRQ_vec+$14
Ibuffe = Ibuffs+$47; end of input buffer
Ram_base = $0300 ; start of user RAM (set as needed, should be page aligned)
Ram_top = $A000 ; end of user RAM+1 (set as needed, should be page aligned)
Ram_top = $7000 ; end of user RAM+1 (set as needed, should be page aligned)
; This start can be changed to suit your system

133
samples/ehbasic_crtc/min_mon.asm
View File

@ -21,9 +21,11 @@ ACIAstatus = IO_AREA+1
ACIAcommand = IO_AREA+2
ACIAcontrol = IO_AREA+3
CPOS_L = $E0 ; Cursor address (low)
CPOS_H = $E1 ; Cursor address (high)
COUTC = $E2 ; Temp storage for char out.
CADDR_L = $E0 ; Cursor address (low)
CADDR_H = $E1 ; Cursor address (high)
C_COL = $E2 ; Cursor column
C_ROW = $E3 ; Cursor row
COUTC = $E4 ; Temp storage for char out.
; now the code. all this does is set up the vectors and interrupt code
@ -42,11 +44,11 @@ RES_vec
;; Initialize the CRTC
LDA #$00 ; Set cursor start to $7000
STA CPOS_L
STA CADDR_L
LDA #$70
STA CPOS_H
STA CADDR_H
;; TODO: Initialize params on CRTC
; Initialize the ACIA
ACIA_init
LDA #$00
@ -92,7 +94,7 @@ LAB_dowarm
JMP LAB_WARM ; do EhBASIC warm start
ACIAout:
ACIAout:
PHA
@loop: LDA ACIAstatus
@ -112,86 +114,50 @@ CRTCout:
STA COUTC ; Store the character going out
JSR ACIAout ; Also echo to terminal for debugging.
;; Is this a CR or LF?
CMP #$0D
BEQ @dolf
CMP #$0A
BEQ @docr
;; Is this a backspace?
;; In parallel, we're maintaining two states:
;; - The address of the cursor, and
;; - The Column/Row of the cursor.
;;
;; The latter state is used to handle scrolling and
;; for knowing how far to back up the cursor
;; for a carriage-return.
;; Backspace
CMP #$08
BEQ @dobs
;; Otherwise, this is a normal character
;; Do normal character stuff.
TYA ; Save Y
PHA
LDA COUTC ; Restore character going out
LDY #$00
STA (CPOS_L),Y
INC CPOS_L
PLA ; Restore Y
TAY
JMP @done
@dolf:
;; Handle a LF
;; Increment CRSR_R.
;; If CRSR_R > ROW_M, scroll..
@docr:
;; Handle a CR
;; Set CRSR_C = 0.
@dobs:
;; 2. 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
;;
@done:
;; Now new cursor Column and Row have been calculated,
;; and we know if we need to scroll.
;;
;; (CPOS_H) = $70 + (row /
BEQ DO_BS
;; Line Feed
CMP #$0a
BEQ DO_BS
;; Carriage Return
CMP #$0d
BEQ DO_CR
;; Any other character
RTS
;; Convert CRSR_C, CRSR_R into Cursor Address.
;; Result stored in CPOS_L,CPOS_H
;;
;; C_POS:
;; ;; Multiply CRSR_R * $28, store result in CPOS_L,CPOS_H
;; LDA CRSR_R ; Copy CRSR_R to CPOS_L
;; STA CPOS_L
;; LDA #$00
;; LDX #$08
;; LSR CPOS_L
;; @cpos1: BCC @cpos2
;; CLC
;; ADC #$28
;; @cpos2: ROR
;; ROR CPOS_L
;; DEX
;; BNE @cpos1
;; STA CPOS_H
;; ;; At this point, CPOS_L,CPOS_H holds the product
;; ;; of CRSR_R and $28. We need to add CRSR_C with
;; ;; an unsigned 16-bit add.
;; CLC
;; LDA CRSR_C
;; ADC CPOS_L
;; STA CPOS_L
;; BCC @noinc ; If carry wasn't set, no need
;; INC CPOS_H ; to increment CPOS_H
;; @noinc:
DO_BS: RTS
DO_LF: RTS
DO_CR: RTS
;; Handle a scroll request
DO_SCROLL:
RTS
;; Decrement the cursor address
INC_CADDR:
INC CADDR_L
BNE @l1 ; Did we increment to 0?
INC CADDR_H ; Yes, also increment high
@l1 RTS
;; Increment the cursor address
DEC_CADDR:
CMP CADDR_L ; Is low alrady 0?
BNE @l1
DEC CADDR_H ; Yes, decrement high
@l1 DEC CADDR_L
RTS
;
; byte in from ACIA. This subroutine will also force
; all lowercase letters to be uppercase.
@ -265,4 +231,3 @@ LAB_mess
.word NMI_vec ; NMI vector
.word RES_vec ; RESET vector
.word IRQ_vec ; IRQ vector