ubee: Fix scanning logic

With this fixed we now get sensible keyboard results.

Also disable the attempt to get back to monitor - it's not as simple as I hoped!

diff --git a/Kernel/platform-ubee/ubee.s b/Kernel/platform-ubee/ubee.s
index 6c35943..575e00b 100644 (file)
--- a/Kernel/platform-ubee/ubee.s
+++ b/Kernel/platform-ubee/ubee.s
@@ -131,6 +131,10 @@ page_codes:
 ; ROM
 ;
 to_monitor:
+           jp to_monitor
+
+           ; Until we figure out how/if we can fix this
+
            xor a                       ; 0 or 1 to keep low 32K right ? */
            out (0x50), a               ; ROMS please
            jp 0xE003                   ; Monitor
@@ -461,14 +465,16 @@ _kbscan:
            in a,(0x0C)
            bit 6,a             ; No light pen signal - no key
            jr z, nokey         ; Fast path exit
+
+jr notlast ; FIXME
+
             ld a, (_lpen_kbd_last)     ; Rather than the slow scan try and
             cp #255            ; test if we are holding down the same key
             jr z, notlast      ; assuming one was held down
             call ispressed     ; see if the key is held down (usual case)
            ld a, (_lpen_kbd_last)
                                ; if so return the last key
-           bit 0,l             ; b = 1 if we found it
-            jr nz, key_return
+            jr z, nokey
 notlast:
            ld l,#57            ; Scan the keys in two banks, the first 57
            ld de,#0x0000
@@ -479,12 +485,12 @@ notlast:
            ld de,#0x03A0       ; and if that fails the last 5 oddities
            call scanner        ; in order to handle shift etc
             ld a,#63
-gotkey:
-           sub b
-           jr key_return
+           jr nz, gotkey
 nokey:
-           ld a,#255
-key_return:
+           ld l,#255
+           ret
+gotkey:
+           sub l
            ld l,a
            ret
 
@@ -519,6 +525,18 @@ ispressed:
 ;
 ;      Returns L holding the count of keys until we found a hit
 ;
+;      Internal use of registers is as follows
+;      A - scratch                             A
+;      B - low update register                 E
+;      C - 6545 control port                   C
+;      DE - from caller                        HL
+;      H - dummy register index                D
+;      L - counter from caller                 B
+;
+; Obscure Z80ism in a,(n) does not affect flags but in r,(c) does. We
+; rely on this for the scanner and scanner exit code so don't mess with the
+; use of in here as we have a cunning plan...
+;
 scanner:
            ld a,#1
            out (0x0b),a                ; character ROM so we can scan
@@ -536,10 +554,12 @@ sethigh:    ld a,#18                      ; update register high
             ld d,#16
 setlow:     out (c),b                  ; set the low byte from the passed address
            out (0x0d),a
-            out (c),h                  ; dummy read to reset
+            out (c),h                  ; dummy reg to reset
             out (0x0d),a
 strobe:     in e,(c)                   ; spin for a strobe
             jp p, strobe
+           ; for the below we could do in f,(c) jr nz but we are sticking
+           ; to documented instructions for the moment even if longer
             in e,(c)
             bit 6,e                    ; did we get a strobe ?
             jr nz,scanner_done
@@ -554,13 +574,14 @@ strobe:     in e,(c)                      ; spin for a strobe
            ;
            ;   L holds the count remaining and thus computes the keycode
            ;   0 means 'we found nothing'
+           ;   Also Z = no luck, NZ = got one
            ;
 scanner_done:
            pop de                      ; recover position we are at
             ld a,#16                   ; lpen reset
             out (0x0c),a
             in a,(0x0d)                        ; VDU reset
-            xor a
+            ld a,#0                    ; Not xor as we are preserving Z
             out (0x0b),a
            ret