mtx: 80 column driver

Use the crtc to do hardware scrolling

diff --git a/Kernel/platform-mtx/vdp.s b/Kernel/platform-mtx/vdp.s
index 9c5ad23..e9938de 100644 (file)
--- a/Kernel/platform-mtx/vdp.s
+++ b/Kernel/platform-mtx/vdp.s
@@ -43,9 +43,13 @@ videopos6:
             ld e, a
             ld d, #0
             add hl, de                 ; and X
+            ld de, (crtcbase)          ; adjust for CRTC base
+            add hl, de
+            ld a, h
+            and #7                     ; wrap
+            ld h, a
             ret
 
-
 ;
 ;      This is a bit different as we support both the vdp1 and the 6845
 ; port
@@ -77,24 +81,87 @@ _clear_across:
             ld a, (_curtty)
             or a
             jp nz, clear_across
+            pop hl
+            pop de
+            pop bc
+            push bc
+            push de
+            push hl
+            call videopos6             ; HL is now the offset we need
+            ld b, c
+clearbyte:
+            ld a, #' '
+            out (0x32), a
+            ld a, #7
+            out (0x32), a
+            ld a, h
+            or #0xc0
+            out (0x31), a
+            ld a, l
+            out (0x30), a
+            inc hl
+            djnz clearbyte
             ret
 
 _clear_lines:
             ld a, (_curtty)
             or a
             jp nz, clear_lines
+            pop hl
+            pop de
+            push de            ; E = line, D = count
+            push hl
+            ld c,d             ; Lines to copy
+            ld d, #0           ; E = y, D = X
+            ld b, #80
+            call videopos6     ; find our offset in HL
+clearonel:
+            push bc
+clearone:
+            ld a, #' '
+            out (0x32), a
+            ld a, #7
+            out (0x33), a
+            ld a, h
+            or #0xc0
+            out (0x31), a
+            ld a, l
+            out (0x30), a
+            inc hl
+             djnz clearone
+            pop bc
+            dec c
+            jr nz, clearonel
             ret
 
 _scroll_up:  ld a, (_curtty)
             or a
             jp nz, scroll_up
+
+            ld hl, (crtcbase)
+            ld de, #80
+do_scroll:
+            add hl, de
+            ld a, #12
+            out (0x38), a
+            ld a, h
+            and #0x07
+            ld h, a
+            out (0x39), a
+            ld a, #13
+            out (0x38), a
+            ld a, l
+            out (0x39), a
+            ld (crtcbase), hl
             ret
 
 _scroll_down:
             ld a, (_curtty)
             or a
             jp nz, scroll_down
-            ret
+            ld hl, (crtcbase)
+            ld de, #0xFF80
+            jr do_scroll
 
 _plot_char:
             ld a, (_curtty)
@@ -126,4 +193,10 @@ _plot_char:
 ;      common space.
 ;
 platform_interrupt_all:
-           ret
+            in a, (2)
+            ret
+
+            .area _DATA
+
+crtcbase:
+           .dw 0