implemented UDTIM routine

STATUS.md

@@ -106,7 +106,7 @@ NOTE: Even the 'DONE' routines won't support features described as missing in on
 | `$FFE1`   | `STOP`   | DONE     |                                                    |
 | `$FFE4`   | `GETIN`  | PARTIAL  | only some devices supported                        |
 | `$FFE7`   | `CLALL`  | DONE     |                                                    |
-| `$FFEA`   | `UDTIM`  | NOT DONE | checking for STOP key present in SCNKEY instead    |
+| `$FFEA`   | `UDTIM`  | DONE     |                                                    |
 | `$FFED`   | `SCREEN` | DONE     |                                                    |
 | `$FFF0`   | `PLOT`   | NOT DONE |                                                    |
 | `$FFF3`   | `IOBASE` | DONE     |                                                    |

c64/kernal/scnkey.s

@@ -204,10 +204,6 @@ ReturnNoKeys:
 
 NoActivityDetected:
 
-	;; Cancel STKEY status
-	lda #$FF
-	sta STKEY ; XXX this variable should be set by UDTIM
-
 	;; So cancel all bucky keys
 	lda key_bucky_state
 	sta key_last_bucky_state
@@ -334,12 +330,6 @@ next_row:
 	;; //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 	;; // Check and flag Non Alphanumeric Keys
 
-	;; Store last row of keyboard scan result,
-	;; so that RUN/STOP etc can be checked easily
-	;; (Compute's Mapping the 64, p27)
-	lda ScanResult+0
-	sta STKEY ; XXX this variable should be set by UDTIM
-
 	;; Store de-bounce data for bucky keys
 	;; (Compute's Mapping the 64, p58-59)
 	lda key_bucky_state

c64/kernal/udtim.s

@@ -9,4 +9,46 @@
 ;;
 
 udtim:
+
+	;; Update jiffy clock. The whole day is $4F1A00 jiffies (24 hours * 60 minutes * 60 seconds * 60 jiffies),
+	;; after this time we have to reset the clock.
+
+	inc TIME+0
+	bne udtim_clock_done
+	inc TIME+1
+	bne udtim_clock_rollover
+	inc TIME+2
+
+	;; FALLTROUGH
+
+udtim_clock_done:
+udtim_update_stkey: ; entry to be used when interrupts are disabled
+
+	;; Another action we have to perform is to copy the last row of keyboard to RAM,
+	;; so that various routines can detect the STOP key press
+	;; XXX scnkey contains similar sequence - deduplicate this!
+	lda #$FF
+	sta CIA1_DDRA ; output
+	lda #$00
+	sta CIA1_DDRB ; input
+
+	lda #$7F
+	sta CIA1_PRA  ; select the last row (bit to 0)
+
+	lda CIA1_PRB  ; read the row
+	sta STKEY
 	rts
+
+udtim_clock_rollover:
+
+	;; At this point TIME+0 has to contain 0,
+	lda TIME+1
+	cmp #$1A
+	bne udtim_clock_done
+	lda TIME+2
+	cmp #$4F
+	bne udtim_clock_done
+	lda #$00
+	sta TIME+2
+	sta TIME+1
+	beq udtim_clock_done ; will always jump